What version of drivers are you using?
Mine is stable with acceptable 3D support and good 2D acceleration. It also suspends to ram
several times a day and this has worked better then my old Ibook.. with either OS X or Linux
on it. Compiz-fusion works well also, the only major problem is that EXA support isn't fast
enough for large videos with 32bit graphics, so I run 16bit. Oh and OpenGL applications still
are ugly when running on compiz.. but their performance isn't affected in a noticable way.
That and it's xrandr support allows me to hotplug external monitors and configure X to use
them on the fly, which is a new experiance for with with open source drivers.
BTW, this is with Debian Unstable/testing on a Dell 1420n.