[T-Mobile Samsung Galaxy S II SGH-T989] ElectricBubble:
General miui 2.6.8 changlog:

[System]

Optimisation - when adjusting the clock minute selection, the clock does not automatically add / subtract

I9100 update to base version ZSLPG

LT18I update to base version 4.1.B.0.431

Honor update to base version B919

Optimisation of the application task management, total available memory and actual physical memory. In addition showing memory occupied by hardware resources.

Fix problem with return key to exit applications does not clean up application from memory even after exiting application using the return key

Fix black screen after call, the volume keys and camera button can wake up the screen

[Phone]

New call, new call reminder supports notification tone, can also be set up with prompts e.g. (Times to be reminded, vibrate on first alert) etc.

Fix problem using Application control (protection) to limit access to dialer and contacts

Fix in some cases the answer call panel disappears

Fix set ringtone for no delay, call still has sound problems

[Contact]

New contact details page, click on the picture to view the ID

New - Contact details page for Birthday information automatically goes to Calendar when pressed on

Optimise selection, editing, large contact picture; generate small icon in dashed box

New contacts Lunar birthday corresponds to the next calendar Date of birth

[Messaging]

New birthday greetings feature, send special birthday message items to friends / family

Optimisation support to search contacts in Messages

Fix (CDMA) cannot prefix number with the "+" number to send a message

[Lock screen, Status bar, Notification bar]

Add Variety lock screen to support the cut-off screen buffer as a picture source (which can unlock effect blinds, folding, etc.)

Add Variety lock screen support using screenshots as a picture source

New Variety lock screen support query web service, and through the use of XPATH to retrieve different parameters

Added support for 3D rotation

[Themes]

Optimised browsing ringtones, previews and download to give a better user experience

Fix new icons in some cases local thumbnails

Fix problems with incorrect theme package size

Fix various FC issues

Fix click the first item in the list view, the title bar will show problems

Fix Desktop theme module cannot be used

Fix problem with backup of font from theme, when restored leads to some garbled issues

[Camera] [MI-ONE]

New video support click on the screen to focus

Optimise the photo compression parameters, default compression has been modified to improve quality (Default Picture size can be changed in settings)

Fix taking photos at 5 megapixels, the photos the edge shows a green and sometimes varied colour line

Optimise video recording now allows a maximum recording of 2 hours continuously

Added support for 16:9 ratio full-screen camera format (See Settings to modify sizes)

[Gallery]

For optimal viewing pictures, slide up and down the picture from side to side

Repair using a picture covering the same picture and thumbnails and real Figure

Fix some unusual colour problems after finishing playing video and returning to the viewfinder interface

[Music]

Added new version of Music player app

[Backup]

Optimise lack of SD card space backup reminders

Repair bulk backup or restore for contacts and MMS causes FC

[Settings]

New functions for stopping current program (press return key) with a longer response time

Add support for majority of original factory settings

[File Manager]

Optimise load efficiency when entering the file search

[Calendar]

New month view and list view, now able to add the Lunar New Year

Optimisation to update the calendar reminder text descriptions

Optimisation to merge multiple calendar birthday entries

Fix problem due to Daylight savings time leads to the Lunar calendar date being incorrect

Sources:

http://miuiandroid.com/community/threads/miui-rom-2-6-8-change-log.16878/

In case you havn't been following the thread Miui 2.6.1 can be found here:

http://goo.im/miui/hercules​