I installed Ubuntu 11.04 shortly after if came out. However, it ran sluggish, in my opinion. Slower than windows on the same computer. This has never been the case up to now. So, I did some Googlin'. Found the link in the title in the Ubuntu forums. In a nut shell:
Don't know if there's a bug report, the only related thing I found was this
Originally Posted by ShadowKyuzo
But i think i just solved it here on my pc.
Do you have Compiz Settings Manager?
I did this and video playback seems normal now:
1. Go to Compiz Settings Manager
2. On the "general" options, go to COMPOSITE
3. Disable "Detect Refresh Rate"
4. Set "Refresh Rate" to 60 (or your monitor's refresh rate)
5. Go back to the "general" options and now go to "OpenGL"
6. Disable "Synchronize to VBlank"
Thanks to the original poster. It help me a bunch.