So, definitely give it a twhirl this week(end) and do let me know what you think!
Download CM12 ROM for T-Mobile Galaxy S2 SGH-T989 (this is the version I used, for latest, you can check here, I put the version I used since sometimes new versions can contain bugs that I did not see.)
Download Android 5.0 Lollipop Gapps (Do not use KitKat Gapps, will not work!) (grab the pico version!!!)
IF YOU HAVE CWM RECOVERY OLDER THAN VERSION 220.127.116.11, UPGRADE your CWM Recovery to latest version by downloading the zip and installing with your CWM recovery OTHERWISE ROM WILL NOT INSTALL!
To install, reboot into recovery, make backup ROM, wipe data/factory reset, install ROM, install Gapps, and reboot. (If for some reason you end up in a bootloop, reboot into recovery, go to Advanced Wipe for TWRP or Mounts & Storage for CWM, format/wipe /system, then re-install ROM.)