Mostly bug fixes. Improves performance Browser performance (I know a few who have been having a hard time browsing certain sites on their PB browser). Improves native PIM functions (E-mail, vchat, Bridge functionality) Android Player/Android Runtime have seen a few improvements as well.
On the technical side, a driver has been seen in the PB that should allow (It has not been enabled yet) USB OTG (On-The-Go) use. Maybe we'll be able to connect a flash drive/usb stick to our tablets, increasing our storage space. Bluetooth audio streaming (dnla) has improved as well as more support for other video formats (Some examples would be playing large movie files (over 1GB)). I still cannot play some of my .mkv movies though. I am pretty happy with the update. I wasn't having that many issues before it came out so.....
There are things I still feel are missing, but they seem to be on the right track.
8520 (v188.8.131.52 Rogers/BES), 9900 (v184.108.40.2063/342 Hybrid[Bell/BIS]), Playbook (v220.127.116.1171)