It depends what you want to do with it. I had one a while ago, personally I wasn't very impressed, so I sold it.
It's OK for general desktop use. 3D performance is non-existent, video playback was poor. Last time I used it (about 2 months ago), I had green dots all over the screen, so the driver is/was crap. Not surprisingly, using the binary mga-hal driver was worse than the open-source X driver (and it also bodged the console when X exited). But, then again, mplayer has a matrox video output module, so presumably it works for some people. YMMV.
Given the choice, I'd avoid it.
