How to fix OS X Lion being unresponsive? After having upgraded to OS X Lion seamlessly, the whole system became unresponsive. Sometimes, I have to wait seconds for keypresses or clicks to have effect, even sound playback or the Dock animation stutters, while strangely the CPU usage remains low. Repairing my disk and its permissions didn't help, upgrading to 10.7.1 neither. Can somebody help?

FYI: I have a 2.3 GHz 13'' MBP with 4 GB RAM.
This kind of thing is a RAM problem 9 times out of 10. Your RAM is constantly being paged in and out to your (relatively slow) hard drive, causing you to wait. THe best solution is to upgrade your RAM or if it's already maxed, consider getting an SSD.