[Samsung Galaxy Nexus] kendong2:
in 4.2 there seems to be more:

bootloader, radio, userdata and (interestingly) bootimg are identical. in recovery some timestamps and fingerprints, nothing exciting:

diff -r takju-jop40c/recovery.img/boot.img-ramdisk/default.prop yakju-jop40c/recovery.img/boot.img-ramdisk/default.prop
16,17c16,17
< ro.build.date=Sat Nov 10 08:27:42 UTC 2012
< ro.build.date.utc=1352536062
---
> ro.build.date=Sat Nov 10 07:53:49 UTC 2012
> ro.build.date.utc=1352534029
20c20
< ro.build.host=vpba13.mtv.corp.google.com
---
> ro.build.host=vpba4.mtv.corp.google.com
24c24
< ro.product.name=takju
---
> ro.product.name=yakju
37,38c37,38
< ro.build.description=takju-user 4.2 JOP40C 527662 release-keys
< ro.build.fingerprint=google/takju/maguro:4.2/JOP40C/527662:user/release-keys
---
> ro.build.description=yakju-user 4.2 JOP40C 527662 release-keys
> ro.build.fingerprint=google/yakju/maguro:4.2/JOP40C/527662:user/release-keys

now for system, first the obvious build.prop:

diff -r takju-jop40c/build.prop yakju-jop40c/build.prop
9,10c9,10
< ro.build.date=Sat Nov 10 08:27:42 UTC 2012
< ro.build.date.utc=1352536062
---
> ro.build.date=Sat Nov 10 07:53:49 UTC 2012
> ro.build.date.utc=1352534029
13c13
< ro.build.host=vpba13.mtv.corp.google.com
---
> ro.build.host=vpba4.mtv.corp.google.com
17c17
< ro.product.name=takju
---
> ro.product.name=yakju
30,31c30,31
< ro.build.description=takju-user 4.2 JOP40C 527662 release-keys
< ro.build.fingerprint=google/takju/maguro:4.2/JOP40C/527662:user/release-keys
---
> ro.build.description=yakju-user 4.2 JOP40C 527662 release-keys
> ro.build.fingerprint=google/yakju/maguro:4.2/JOP40C/527662:user/release-keys

then there is the other obvious, Wallet.apk:

Only in takju-jop40c/app: Wallet.apk

still nothing exciting up to here. and now the rest, differing binary files:

Binary files takju-jop40c/app/LiveWallpapers.apk and yakju-jop40c/app/LiveWallpapers.apk differ
Binary files takju-jop40c/app/Videos.apk and yakju-jop40c/app/Videos.apk differ
Binary files takju-jop40c/app/VisualizationWallpapers.apk and yakju-jop40c/app/VisualizationWallpapers.apk differ
Binary files takju-jop40c/bin/debuggerd and yakju-jop40c/bin/debuggerd differ
Binary files takju-jop40c/bin/mdnsd and yakju-jop40c/bin/mdnsd differ
Binary files takju-jop40c/etc/NOTICE.html.gz and yakju-jop40c/etc/NOTICE.html.gz differ
Binary files takju-jop40c/etc/recovery-resource.dat and yakju-jop40c/etc/recovery-resource.dat differ
Binary files takju-jop40c/framework/am.jar and yakju-jop40c/framework/am.jar differ
Binary files takju-jop40c/framework/am.odex and yakju-jop40c/framework/am.odex differ
Binary files takju-jop40c/framework/android.policy.jar and yakju-jop40c/framework/android.policy.jar differ
Binary files takju-jop40c/framework/android.policy.odex and yakju-jop40c/framework/android.policy.odex differ
Binary files takju-jop40c/framework/android.test.runner.jar and yakju-jop40c/framework/android.test.runner.jar differ
Binary files takju-jop40c/framework/android.test.runner.odex and yakju-jop40c/framework/android.test.runner.odex differ
Binary files takju-jop40c/framework/apache-xml.jar and yakju-jop40c/framework/apache-xml.jar differ
Binary files takju-jop40c/framework/apache-xml.odex and yakju-jop40c/framework/apache-xml.odex differ
Binary files takju-jop40c/framework/bmgr.jar and yakju-jop40c/framework/bmgr.jar differ
Binary files takju-jop40c/framework/bmgr.odex and yakju-jop40c/framework/bmgr.odex differ
Binary files takju-jop40c/framework/bouncycastle.jar and yakju-jop40c/framework/bouncycastle.jar differ
Binary files takju-jop40c/framework/bouncycastle.odex and yakju-jop40c/framework/bouncycastle.odex differ
Binary files takju-jop40c/framework/bu.jar and yakju-jop40c/framework/bu.jar differ
Binary files takju-jop40c/framework/bu.odex and yakju-jop40c/framework/bu.odex differ
Binary files takju-jop40c/framework/com.android.future.usb.accessory.jar and yakju-jop40c/framework/com.android.future.usb.accessory.jar differ
Binary files takju-jop40c/framework/com.android.future.usb.accessory.odex and yakju-jop40c/framework/com.android.future.usb.accessory.odex differ
Binary files takju-jop40c/framework/com.android.location.provider.jar and yakju-jop40c/framework/com.android.location.provider.jar differ
Binary files takju-jop40c/framework/com.android.location.provider.odex and yakju-jop40c/framework/com.android.location.provider.odex differ
Binary files takju-jop40c/framework/com.android.nfc_extras.jar and yakju-jop40c/framework/com.android.nfc_extras.jar differ
Binary files takju-jop40c/framework/com.android.nfc_extras.odex and yakju-jop40c/framework/com.android.nfc_extras.odex differ
Binary files takju-jop40c/framework/com.google.android.maps.jar and yakju-jop40c/framework/com.google.android.maps.jar differ
Binary files takju-jop40c/framework/com.google.android.maps.odex and yakju-jop40c/framework/com.google.android.maps.odex differ
Binary files takju-jop40c/framework/com.google.android.media.effects.jar and yakju-jop40c/framework/com.google.android.media.effects.jar differ
Binary files takju-jop40c/framework/com.google.android.media.effects.odex and yakju-jop40c/framework/com.google.android.media.effects.odex differ
Binary files takju-jop40c/framework/com.google.widevine.software.drm.jar and yakju-jop40c/framework/com.google.widevine.software.drm.jar differ
Binary files takju-jop40c/framework/com.google.widevine.software.drm.odex and yakju-jop40c/framework/com.google.widevine.software.drm.odex differ
Binary files takju-jop40c/framework/content.jar and yakju-jop40c/framework/content.jar differ
Binary files takju-jop40c/framework/content.odex and yakju-jop40c/framework/content.odex differ
Binary files takju-jop40c/framework/core.jar and yakju-jop40c/framework/core.jar differ
Binary files takju-jop40c/framework/core-junit.jar and yakju-jop40c/framework/core-junit.jar differ
Binary files takju-jop40c/framework/core-junit.odex and yakju-jop40c/framework/core-junit.odex differ
Binary files takju-jop40c/framework/core.odex and yakju-jop40c/framework/core.odex differ
Binary files takju-jop40c/framework/ext.jar and yakju-jop40c/framework/ext.jar differ
Binary files takju-jop40c/framework/ext.odex and yakju-jop40c/framework/ext.odex differ
Binary files takju-jop40c/framework/framework.jar and yakju-jop40c/framework/framework.jar differ
Binary files takju-jop40c/framework/framework.odex and yakju-jop40c/framework/framework.odex differ
Binary files takju-jop40c/framework/ime.jar and yakju-jop40c/framework/ime.jar differ
Binary files takju-jop40c/framework/ime.odex and yakju-jop40c/framework/ime.odex differ
Binary files takju-jop40c/framework/input.jar and yakju-jop40c/framework/input.jar differ
Binary files takju-jop40c/framework/input.odex and yakju-jop40c/framework/input.odex differ
Binary files takju-jop40c/framework/javax.obex.jar and yakju-jop40c/framework/javax.obex.jar differ
Binary files takju-jop40c/framework/javax.obex.odex and yakju-jop40c/framework/javax.obex.odex differ
Binary files takju-jop40c/framework/mms-common.jar and yakju-jop40c/framework/mms-common.jar differ
Binary files takju-jop40c/framework/mms-common.odex and yakju-jop40c/framework/mms-common.odex differ
Binary files takju-jop40c/framework/monkey.jar and yakju-jop40c/framework/monkey.jar differ
Binary files takju-jop40c/framework/monkey.odex and yakju-jop40c/framework/monkey.odex differ
Binary files takju-jop40c/framework/pm.jar and yakju-jop40c/framework/pm.jar differ
Binary files takju-jop40c/framework/pm.odex and yakju-jop40c/framework/pm.odex differ
Binary files takju-jop40c/framework/requestsync.jar and yakju-jop40c/framework/requestsync.jar differ
Binary files takju-jop40c/framework/requestsync.odex and yakju-jop40c/framework/requestsync.odex differ
Binary files takju-jop40c/framework/send_bug.jar and yakju-jop40c/framework/send_bug.jar differ
Binary files takju-jop40c/framework/send_bug.odex and yakju-jop40c/framework/send_bug.odex differ
Binary files takju-jop40c/framework/services.jar and yakju-jop40c/framework/services.jar differ
Binary files takju-jop40c/framework/services.odex and yakju-jop40c/framework/services.odex differ
Binary files takju-jop40c/framework/settings.jar and yakju-jop40c/framework/settings.jar differ
Binary files takju-jop40c/framework/settings.odex and yakju-jop40c/framework/settings.odex differ
Binary files takju-jop40c/framework/svc.jar and yakju-jop40c/framework/svc.jar differ
Binary files takju-jop40c/framework/svc.odex and yakju-jop40c/framework/svc.odex differ
Binary files takju-jop40c/framework/telephony-common.jar and yakju-jop40c/framework/telephony-common.jar differ
Binary files takju-jop40c/framework/telephony-common.odex and yakju-jop40c/framework/telephony-common.odex differ
Binary files takju-jop40c/framework/uiautomator.jar and yakju-jop40c/framework/uiautomator.jar differ
Binary files takju-jop40c/framework/uiautomator.odex and yakju-jop40c/framework/uiautomator.odex differ
Binary files takju-jop40c/lib/libbcc.sha1.so and yakju-jop40c/lib/libbcc.sha1.so differ
Binary files takju-jop40c/lib/libbcc.so and yakju-jop40c/lib/libbcc.so differ
Binary files takju-jop40c/lib/libbcinfo.so and yakju-jop40c/lib/libbcinfo.so differ
Binary files takju-jop40c/lib/libchromium_net.so and yakju-jop40c/lib/libchromium_net.so differ
Binary files takju-jop40c/lib/libmdnssd.so and yakju-jop40c/lib/libmdnssd.so differ
Binary files takju-jop40c/lib/libmllite.so and yakju-jop40c/lib/libmllite.so differ
Binary files takju-jop40c/lib/libpatts_engine_jni_api.so and yakju-jop40c/lib/libpatts_engine_jni_api.so differ
Binary files takju-jop40c/lib/libstagefright_soft_aacdec.so and yakju-jop40c/lib/libstagefright_soft_aacdec.so differ
Binary files takju-jop40c/lib/libstagefright_soft_aacenc.so and yakju-jop40c/lib/libstagefright_soft_aacenc.so differ
Binary files takju-jop40c/lib/libwebcore.so and yakju-jop40c/lib/libwebcore.so differ
Binary files takju-jop40c/lib/libwebrtc_audio_preprocessing.so and yakju-jop40c/lib/libwebrtc_audio_preprocessing.so differ

i don't feel like disecting these, so if anyone feels the need to do so, have fun...