Fix lag in full screen flash videos
I just installed Ubuntu 11.04 and I find it quite nice. The only real problem was, that flash videos was lagging out in full screen. To solve this you either have to disable compiz or disable hardware acceleration for the flash player. I choice the later option. Here is have you do it: Edit/create the file /etc/adobe/mms.cfg (create the folder if it dosn't exists). Add OverrideGPUValidation=1 on a seperate line in that file and save. Restart your browser.
Update July 5 2011: Or you can buy an ATI graphic card.