[HTC Sensation] bxlegend:
Here's a brief diff of the two after unzipping:

Files /cm-10-20130421-NIGHTLY-pyramid/boot.img and /cm-10-20130429-NIGHTLY-pyramid/boot.img differ
Files /cm-10-20130421-NIGHTLY-pyramid/META-INF/CERT.RSA and /cm-10-20130429-NIGHTLY-pyramid/META-INF/CERT.RSA differ
Files /cm-10-20130421-NIGHTLY-pyramid/META-INF/CERT.SF and /cm-10-20130429-NIGHTLY-pyramid/META-INF/CERT.SF differ
Files /cm-10-20130421-NIGHTLY-pyramid/META-INF/com/android/metadata and /cm-10-20130429-NIGHTLY-pyramid/META-INF/com/android/metadata differ
Files /cm-10-20130421-NIGHTLY-pyramid/META-INF/MANIFEST.MF and /cm-10-20130429-NIGHTLY-pyramid/META-INF/MANIFEST.MF differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/app/ApplicationsProvider.apk and /cm-10-20130429-NIGHTLY-pyramid/system/app/ApplicationsProvider.apk differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/app/BackupRestoreConfirmation.apk and /cm-10-20130429-NIGHTLY-pyramid/system/app/BackupRestoreConfirmation.apk differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/app/Bluetooth.apk and /cm-10-20130429-NIGHTLY-pyramid/system/app/Bluetooth.apk differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/app/Browser.apk and /cm-10-20130429-NIGHTLY-pyramid/system/app/Browser.apk differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/app/Calculator.apk and /cm-10-20130429-NIGHTLY-pyramid/system/app/Calculator.apk differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/app/Calendar.apk and /cm-10-20130429-NIGHTLY-pyramid/system/app/Calendar.apk differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/app/CalendarProvider.apk and /cm-10-20130429-NIGHTLY-pyramid/system/app/CalendarProvider.apk differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/app/CertInstaller.apk and /cm-10-20130429-NIGHTLY-pyramid/system/app/CertInstaller.apk differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/app/CMWallpapers.apk and /cm-10-20130429-NIGHTLY-pyramid/system/app/CMWallpapers.apk differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/app/Contacts.apk and /cm-10-20130429-NIGHTLY-pyramid/system/app/Contacts.apk differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/app/ContactsProvider.apk and /cm-10-20130429-NIGHTLY-pyramid/system/app/ContactsProvider.apk differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/app/DefaultContainerService.apk and /cm-10-20130429-NIGHTLY-pyramid/system/app/DefaultContainerService.apk differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/app/DownloadProvider.apk and /cm-10-20130429-NIGHTLY-pyramid/system/app/DownloadProvider.apk differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/app/DownloadProviderUi.apk and /cm-10-20130429-NIGHTLY-pyramid/system/app/DownloadProviderUi.apk differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/app/DrmProvider.apk and /cm-10-20130429-NIGHTLY-pyramid/system/app/DrmProvider.apk differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/app/HoloSpiralWallpaper.apk and /cm-10-20130429-NIGHTLY-pyramid/system/app/HoloSpiralWallpaper.apk differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/app/HTMLViewer.apk and /cm-10-20130429-NIGHTLY-pyramid/system/app/HTMLViewer.apk differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/app/InputDevices.apk and /cm-10-20130429-NIGHTLY-pyramid/system/app/InputDevices.apk differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/app/KeyChain.apk and /cm-10-20130429-NIGHTLY-pyramid/system/app/KeyChain.apk differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/app/LatinIME.apk and /cm-10-20130429-NIGHTLY-pyramid/system/app/LatinIME.apk differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/app/LiveWallpapers.apk and /cm-10-20130429-NIGHTLY-pyramid/system/app/LiveWallpapers.apk differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/app/LiveWallpapersPicker.apk and /cm-10-20130429-NIGHTLY-pyramid/system/app/LiveWallpapersPicker.apk differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/app/MagicSmokeWallpapers.apk and /cm-10-20130429-NIGHTLY-pyramid/system/app/MagicSmokeWallpapers.apk differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/app/MediaProvider.apk and /cm-10-20130429-NIGHTLY-pyramid/system/app/MediaProvider.apk differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/app/Mms.apk and /cm-10-20130429-NIGHTLY-pyramid/system/app/Mms.apk differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/app/PackageInstaller.apk and /cm-10-20130429-NIGHTLY-pyramid/system/app/PackageInstaller.apk differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/app/Phone.apk and /cm-10-20130429-NIGHTLY-pyramid/system/app/Phone.apk differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/app/Provision.apk and /cm-10-20130429-NIGHTLY-pyramid/system/app/Provision.apk differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/app/QuickSearchBox.apk and /cm-10-20130429-NIGHTLY-pyramid/system/app/QuickSearchBox.apk differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/app/Settings.apk and /cm-10-20130429-NIGHTLY-pyramid/system/app/Settings.apk differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/app/SettingsProvider.apk and /cm-10-20130429-NIGHTLY-pyramid/system/app/SettingsProvider.apk differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/app/SharedStorageBackup.apk and /cm-10-20130429-NIGHTLY-pyramid/system/app/SharedStorageBackup.apk differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/app/SoundRecorder.apk and /cm-10-20130429-NIGHTLY-pyramid/system/app/SoundRecorder.apk differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/app/SpareParts.apk and /cm-10-20130429-NIGHTLY-pyramid/system/app/SpareParts.apk differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/app/Stk.apk and /cm-10-20130429-NIGHTLY-pyramid/system/app/Stk.apk differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/app/SystemUI.apk and /cm-10-20130429-NIGHTLY-pyramid/system/app/SystemUI.apk differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/app/TelephonyProvider.apk and /cm-10-20130429-NIGHTLY-pyramid/system/app/TelephonyProvider.apk differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/app/Torch.apk and /cm-10-20130429-NIGHTLY-pyramid/system/app/Torch.apk differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/app/UserDictionaryProvider.apk and /cm-10-20130429-NIGHTLY-pyramid/system/app/UserDictionaryProvider.apk differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/app/VisualizationWallpapers.apk and /cm-10-20130429-NIGHTLY-pyramid/system/app/VisualizationWallpapers.apk differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/app/VoiceDialer.apk and /cm-10-20130429-NIGHTLY-pyramid/system/app/VoiceDialer.apk differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/app/VpnDialogs.apk and /cm-10-20130429-NIGHTLY-pyramid/system/app/VpnDialogs.apk differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/app/WAPPushManager.apk and /cm-10-20130429-NIGHTLY-pyramid/system/app/WAPPushManager.apk differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/bin/debuggerd and /cm-10-20130429-NIGHTLY-pyramid/system/bin/debuggerd differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/bin/mdnsd and /cm-10-20130429-NIGHTLY-pyramid/system/bin/mdnsd differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/bin/mkyaffs2image and /cm-10-20130429-NIGHTLY-pyramid/system/bin/mkyaffs2image differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/build.prop and /cm-10-20130429-NIGHTLY-pyramid/system/build.prop differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/etc/build-manifest.xml and /cm-10-20130429-NIGHTLY-pyramid/system/etc/build-manifest.xml differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/etc/CHANGES.txt and /cm-10-20130429-NIGHTLY-pyramid/system/etc/CHANGES.txt differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/etc/NOTICE.html.gz and /cm-10-20130429-NIGHTLY-pyramid/system/etc/NOTICE.html.gz differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/etc/security/otacerts.zip and /cm-10-20130429-NIGHTLY-pyramid/system/etc/security/otacerts.zip differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/framework/am.jar and /cm-10-20130429-NIGHTLY-pyramid/system/framework/am.jar differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/framework/android.policy.jar and /cm-10-20130429-NIGHTLY-pyramid/system/framework/android.policy.jar differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/framework/android.test.runner.jar and /cm-10-20130429-NIGHTLY-pyramid/system/framework/android.test.runner.jar differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/framework/apache-xml.jar and /cm-10-20130429-NIGHTLY-pyramid/system/framework/apache-xml.jar differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/framework/bmgr.jar and /cm-10-20130429-NIGHTLY-pyramid/system/framework/bmgr.jar differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/framework/bouncycastle.jar and /cm-10-20130429-NIGHTLY-pyramid/system/framework/bouncycastle.jar differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/framework/bu.jar and /cm-10-20130429-NIGHTLY-pyramid/system/framework/bu.jar differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/framework/com.android.future.usb.accessory.jar and /cm-10-20130429-NIGHTLY-pyramid/system/framework/com.android.future.usb.accessory.jar differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/framework/com.android.location.provider.jar and /cm-10-20130429-NIGHTLY-pyramid/system/framework/com.android.location.provider.jar differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/framework/content.jar and /cm-10-20130429-NIGHTLY-pyramid/system/framework/content.jar differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/framework/core.jar and /cm-10-20130429-NIGHTLY-pyramid/system/framework/core.jar differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/framework/core-junit.jar and /cm-10-20130429-NIGHTLY-pyramid/system/framework/core-junit.jar differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/framework/ext.jar and /cm-10-20130429-NIGHTLY-pyramid/system/framework/ext.jar differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/framework/framework.jar and /cm-10-20130429-NIGHTLY-pyramid/system/framework/framework.jar differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/framework/framework2.jar and /cm-10-20130429-NIGHTLY-pyramid/system/framework/framework2.jar differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/framework/framework-res.apk and /cm-10-20130429-NIGHTLY-pyramid/system/framework/framework-res.apk differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/framework/ime.jar and /cm-10-20130429-NIGHTLY-pyramid/system/framework/ime.jar differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/framework/input.jar and /cm-10-20130429-NIGHTLY-pyramid/system/framework/input.jar differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/framework/javax.obex.jar and /cm-10-20130429-NIGHTLY-pyramid/system/framework/javax.obex.jar differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/framework/monkey.jar and /cm-10-20130429-NIGHTLY-pyramid/system/framework/monkey.jar differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/framework/pm.jar and /cm-10-20130429-NIGHTLY-pyramid/system/framework/pm.jar differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/framework/requestsync.jar and /cm-10-20130429-NIGHTLY-pyramid/system/framework/requestsync.jar differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/framework/services.jar and /cm-10-20130429-NIGHTLY-pyramid/system/framework/services.jar differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/framework/svc.jar and /cm-10-20130429-NIGHTLY-pyramid/system/framework/svc.jar differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/framework/uiautomator.jar and /cm-10-20130429-NIGHTLY-pyramid/system/framework/uiautomator.jar differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/lib/libaudioflinger.so and /cm-10-20130429-NIGHTLY-pyramid/system/lib/libaudioflinger.so differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/lib/libbcc.so and /cm-10-20130429-NIGHTLY-pyramid/system/lib/libbcc.so differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/lib/libbcc.so.sha1 and /cm-10-20130429-NIGHTLY-pyramid/system/lib/libbcc.so.sha1 differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/lib/libbcinfo.so and /cm-10-20130429-NIGHTLY-pyramid/system/lib/libbcinfo.so differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/lib/libchromium_net.so and /cm-10-20130429-NIGHTLY-pyramid/system/lib/libchromium_net.so differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/lib/libmdnssd.so and /cm-10-20130429-NIGHTLY-pyramid/system/lib/libmdnssd.so differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/lib/libstagefright_soft_aacdec.so and /cm-10-20130429-NIGHTLY-pyramid/system/lib/libstagefright_soft_aacdec.so differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/lib/libstagefright_soft_aacenc.so and /cm-10-20130429-NIGHTLY-pyramid/system/lib/libstagefright_soft_aacenc.so differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/lib/libwebcore.so and /cm-10-20130429-NIGHTLY-pyramid/system/lib/libwebcore.so differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/lib/libwebrtc_audio_preprocessing.so and /cm-10-20130429-NIGHTLY-pyramid/system/lib/libwebrtc_audio_preprocessing.so differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/xbin/nano and /cm-10-20130429-NIGHTLY-pyramid/system/xbin/nano differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/xbin/openvpn and /cm-10-20130429-NIGHTLY-pyramid/system/xbin/openvpn differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/xbin/oprofiled and /cm-10-20130429-NIGHTLY-pyramid/system/xbin/oprofiled differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/xbin/powertop and /cm-10-20130429-NIGHTLY-pyramid/system/xbin/powertop differ
Files /cm-10-20130421-NIGHTLY-pyramid/system/xbin/vim and /cm-10-20130429-NIGHTLY-pyramid/system/xbin/vim differ

If you do a more detailed diff, you can see exactly what has changed in the files that are not compressed.

If nothing changed a nightly would not be built.

You're picking at straws here. I'm sure everyone knows what was meant.