I too have seen similar. The system is especially bad whenever it is doing a fancy transition, like trying to display a menu, switch tasks, etc.

I've tried reboots and but it hasn't helped. I've checked top and I see nothing significant in it. Almost everything installed is from extras-testing with some of my own apps out of extras-devel.

I've got jabber, either skype or sip enabled, and occasionally The One Ring. I cannot remember if I've seen it since I've disabled some desktop widgets. I had calendar, RSS, some apps, data plan monitor, ip monitor, omweather, location, etc and removed a couple of them.