I recently updated to Ubuntu Lucid and immediately noticed UI performance degradation after using it for a short while. The sluggish performance affected window switching and scrolling in Firefox/Chrome/Evince etc. Nothing on my system indicated a memory leak or chewed-up processor.

I searched Ubuntu's bug tracking system and came across this post, which indicated the using the latest kernel version fix the problem. After following the steps here to update my kernel, my system runs as fast as ever. Hopefully other users experience my situation will stumble across this post and find it helpful.