I recently upgraded my dad's system to 9.10 and sadly boxee has taken a major hit in performance. The system is a Pentium D 3.0ghz from the end of the P4 era. It also has a capable nVidia AGP card. I should mention that I tried reinstalling boxee with no change in performance after the distro upgrade.
So what's the deal? Before upgrading my dad was able to watch anything below 720p and even some moderate bitrate 720p encodes (scaled down to SD). Now, even moving the mouse across the screen in boxee's UI is painful to watch, without a video playing! It does manage to play videos like SD mpeg4 and mpeg2 encodes but only about 80-90% speed with the rest frame dropped. The audio loses sync for all videos now as well.