T-Mobile users with the Samsung Galaxy S II will be receiving an incremental update to Gingerbread very soon. The update brings the phone to Android version 2.3.6 / Software version T989UVLDE. Here's a breakdown of the changes and fixes:

Improvements:
  • Random reboot/power off fixed
  • Device stability improvements
  • Qualcomm chip patch
  • Google Security fixes


Prerequisites
  • Android version 2.3.6 / Software version T989UVKL1 update
  • At least 50% battery life


To do a manual update, head to Settings > Software Update.

Source: T-Mobile