Never had a problem with Maverick, always very fast. I upgrade to Natty and the graphics seem to be very lagged. CPU, load, and memory usage is low, all graphics are choppy and lagged though. I have the proprietary driver installed and everything.
Alt-Tabbing takes 3-5 seconds for the dialog to popup, zooming in with compiz zoom makes things very slow. I never had any of these problems with 10.10