[LG Optimus 4X HD] tnsantos:
I'll try it right now and will report back here asap.

Windows Explorer still reports 1MB/s using UMS mode. MTP mode is much faster. :S

Weird.

Here is a logcat:

D/VoldConnector( 297): SND -> {volume shared /mnt/sdcard ums} {null}
[B]D/VoldCmdListener( 144): volume shared /mnt/sdcard ums
D/VoldConnector( 297): RCV <- {400 Failed to determine share enable state (No such file or directory)}
D/VoldConnector( 297): RSP <- {400 Failed to determine share enable state (No such file or directory)}[/B]
[COLOR="Red"][B]E/MountService( 297): Failed to read response to volume shared /mnt/sdcard ums[/B][/COLOR]
I/PowerManagerService( 297): setTargetLocked mask=2 curValue=127.0 target=105 targetValue=105 delta=-0.36666667 nominalCurrentValue=127
D/PhoneStatusBar( 390): disable: < expand* icons alerts ticker* system_info BACK HOME recent* clock >
W/InputManagerService( 297): Window already focused, ignoring focus gain of: com.android.internal.view.IInputMethodClient$Stub$Proxy@42536350
D/PhoneStatusBar( 390): disable: < expand icons alerts ticker system_info back* home* recent clock >
I/ActivityManager( 297): No longer want com.google.android.gm (pid 12827): hidden #16
[B]D/VoldCmdListener( 144): volume unshare /mnt/sdcard/external_sd ums
D/Vold ( 144): Volume sdcard state changing 7 (Shared-Unmounted) -> 1 (Idle-Unmounted)
D/VoldConnector( 297): RCV <- {605 Volume sdcard /mnt/sdcard/external_sd state changed from 7 (Shared-Unmounted) to 1 (Idle-Unmounted)}[/B]
D/MountService( 297): sendStorageIntent Intent { act=android.intent.action.MEDIA_UNSHARED dat=file:///mnt/sdcard/external_sd (has extras) }
D/MountService( 297): volume state changed for /mnt/sdcard/external_sd (shared -> unmounted)
I/StorageNotification( 390): Media {/mnt/sdcard/external_sd} state changed from {shared} -> {unmounted}
[B]D/VoldConnector( 297): SND -> {volume shared /mnt/sdcard ums} {null}
D/MountService( 297): sendStorageIntent Intent { act=android.intent.action.MEDIA_UNMOUNTED dat=file:///mnt/sdcard/external_sd (has extras) }
D/VoldCmdListener( 144): volume shared /mnt/sdcard ums
D/VoldConnector( 297): RCV <- {400 Failed to determine share enable state (No such file or directory)}
D/VoldConnector( 297): RSP <- {400 Failed to determine share enable state (No such file or directory)}[/B]
[COLOR="red"][B]E/MountService( 297): Failed to read response to volume shared /mnt/sdcard ums[/B][/COLOR]
I/Vold (13235): Vold 2.1 (the revenge) firing up
D/Vold (13235): Volume sdcard state changing -1 (Initializing) -> 0 (No-Media)
I/DirectVolume(13235): [LGE][VOLD][DirectVolume.cpp][handleDiskAdded()] devpath :/devices/platform/sdhci-tegra.2/mmc_host/mmc2/mmc2:b368/block/mmcblk1
D/Vold (13235): Volume sdcard state changing 0 (No-Media) -> 2 (Pending)
I/DirectVolume( 144): [LGE][VOLD][DirectVolume.cpp][handleDiskAdded()] devpath :/devices/platform/sdhci-tegra.2/mmc_host/mmc2/mmc2:b368/block/mmcblk1
D/Vold ( 144): Volume sdcard state changing 1 (Idle-Unmounted) -> 2 (Pending)
D/VoldConnector( 297): RCV <- {605 Volume sdcard /mnt/sdcard/external_sd state changed from 1 (Idle-Unmounted) to 2 (Pending)}
D/VoldConnector( 297): RCV <- {630 Volume sdcard /mnt/sdcard/external_sd disk inserted (179:16)}
I/DirectVolume(13235): [LGE][VOLD][DirectVolume.cpp][handlePartitionAdded()] devpath :/devices/platform/sdhci-tegra.2/mmc_host/mmc2/mmc2:b368/block/mmcblk1/mmcblk1p1
D/Vold (13235): Volume sdcard state changing 2 (Pending) -> 1 (Idle-Unmounted)
I/DirectVolume( 144): [LGE][VOLD][DirectVolume.cpp][handlePartitionAdded()] devpath :/devices/platform/sdhci-tegra.2/mmc_host/mmc2/mmc2:b368/block/mmcblk1/mmcblk1p1
D/Vold ( 144): Volume sdcard state changing 2 (Pending) -> 1 (Idle-Unmounted)
D/VoldConnector( 297): RCV <- {605 Volume sdcard /mnt/sdcard/external_sd state changed from 2 (Pending) to 1 (Idle-Unmounted)}
[COLOR="red"][B]E/SocketListener(13235): Obtaining file descriptor socket 'vold' failed: No such file or directory[/B][/COLOR]
[COLOR="red"][B]E/Vold (13235): Unable to start CommandListener (No such file or directory)[/B][/COLOR]
W/MountService( 297): Duplicate state transition (unmounted -> unmounted) for /mnt/sdcard/external_sd
D/MountService( 297): sendStorageIntent Intent { act=android.intent.action.MEDIA_UNMOUNTED dat=file:///mnt/sdcard/external_sd (has extras) }
D/VoldConnector( 297): SND -> {volume mount /mnt/sdcard/external_sd} {null}
D/VoldCmdListener( 144): volume mount /mnt/sdcard/external_sd
I/Vold ( 144): /dev/block/vold/179:17 being considered for volume sdcard
D/Vold ( 144): Volume sdcard state changing 1 (Idle-Unmounted) -> 3 (Checking)
D/VoldConnector( 297): RCV <- {605 Volume sdcard /mnt/sdcard/external_sd state changed from 1 (Idle-Unmounted) to 3 (Checking)}
D/MountService( 297): volume state changed for /mnt/sdcard/external_sd (unmounted -> checking)
I/StorageNotification( 390): Media {/mnt/sdcard/external_sd} state changed from {unmounted} -> {checking}
D/MountService( 297): sendStorageIntent Intent { act=android.intent.action.MEDIA_CHECKING dat=file:///mnt/sdcard/external_sd (has extras) }
I/Vold ( 144): Filesystem check completed OK
I/Vold ( 144): Device /dev/block/vold/179:17, target /mnt/sdcard/external_sd mounted @ /mnt/secure/staging
D/Vold ( 144): Volume sdcard state changing 3 (Checking) -> 4 (Mounted)
D/VoldConnector( 297): RCV <- {605 Volume sdcard /mnt/sdcard/external_sd state changed from 3 (Checking) to 4 (Mounted)}
D/MountService( 297): volume state changed for /mnt/sdcard/external_sd (checking -> mounted)
I/StorageNotification( 390): Media {/mnt/sdcard/external_sd} state changed from {checking} -> {mounted}
D/MountService( 297): sendStorageIntent Intent { act=android.intent.action.MEDIA_MOUNTED dat=file:///mnt/sdcard/external_sd (has extras) }
D/VoldConnector( 297): RCV <- {200 volume operation succeeded}
D/VoldConnector( 297): RSP <- {200 volume operation succeeded}
I/ActivityManager( 297): Start proc com.google.android.apps.uploader for broadcast com.google.android.apps.uploader/.ConnectivityBroadcastReceiver: pid=13273 uid=10048 gids={3003}
I/ActivityManager( 297): Start proc com.metago.astro for activity com.metago.astro/.MainActivity: pid=13288 uid=10113 gids={3003, 1015}
I/ActivityManager( 297): START {act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] flg=0x13210000 cmp=com.metago.astro/.MainActivity bnds=[360,864][540,1089] (has extras)} from pid 13288
W/InputManagerService( 297): Starting input on non-focused client com.android.internal.view.IInputMethodClient$Stub$Proxy@41e565b8 (uid=10113 pid=13288)
W/InputManagerService( 297): Client not active, ignoring focus gain of: com.android.internal.view.IInputMethodClient$Stub$Proxy@426f6580
I/ActivityManager( 297): Start proc android.process.acore for content provider com.android.providers.contacts/.call.CallLogProvider: pid=13352 uid=10001 gids={3003, 1015, 1023, 4002}
I/ActivityManager( 297): No longer want com.google.android.gsf.login (pid 12549): hidden #16
D/ConnectivityService( 297): getMobileDataEnabled returning false
I/PowerManagerService( 297): setTargetLocked mask=2 curValue=105.0 target=101 targetValue=101 delta=-0.06666667 nominalCurrentValue=105
I/ActivityManager( 297): START {act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] flg=0x10008000 cmp=com.android.settings/.UsbSettings bnds=[0,318][720,446]} from pid -1
I/ActivityManager( 297): Start proc com.android.settings for activity com.android.settings/.UsbSettings: pid=13383 uid=1000 gids={3003, 1015, 3002, 3001, 1007, 1004, 2002, 1023, 4002, 1006, 3007}
I/ActivityManager( 297): No longer want com.facebook.katana (pid 8129): hidden #16
I/ActivityManager( 297): No longer want com.google.android.apps.maps:FriendService (pid 13050): hidden #16
W/ActivityManager( 297): Scheduling restart of crashed service com.facebook.katana/.service.MediaUploadService in 5000ms
D/VoldConnector( 297): SND -> {volume unshare /mnt/sdcard ums} {null}
D/VoldCmdListener( 144): volume unshare /mnt/sdcard ums
D/VoldConnector( 297): RCV <- {406 volume operation failed (No such file or directory)}
D/VoldConnector( 297): RSP <- {406 volume operation failed (No such file or directory)}
[COLOR="Red"]E/MountService( 297): Failed to share/unshare
E/MountService( 297): com.android.server.NativeDaemonConnectorException: Cmd {volume unshare /mnt/sdcard ums} failed with code 406 : {volume operation failed (No such file or directory)}
E/MountService( 297):	at com.android.server.NativeDaemonConnector.doCommandLocked(NativeDaemonConnector.java:287)
E/MountService( 297):	at com.android.server.NativeDaemonConnector.doCommand(NativeDaemonConnector.java:247)
E/MountService( 297):	at com.android.server.MountService.doShareUnshareVolume(MountService.java:575)
E/MountService( 297):	at com.android.server.MountService.setUsbMassStorageEnabled(MountService.java:1369)
E/MountService( 297):	at android.os.storage.IMountService$Stub.onTransact(IMountService.java:922)
E/MountService( 297):	at android.os.Binder.execTransact(Binder.java:338)
E/MountService( 297):	at dalvik.system.NativeStart.run(Native Method)[/COLOR]