I've had mine since August. It seems to be a great car. The cargo room is great, lots of head room, back seats are pretty comfortable, the seat height is great for seeing the road. The seats are very supportive - my wife needed an Obus form when she was a passanger in our 03 Camry - but not in the Matrix. So far all the bits and bobs are working and I haven't had a problem with the compartment door under the shifter but it does seem to be a reasonably common problem. The car has all the power that I need, although I don't drive as spirited as some so you may want to hear from some "spirited" drivers.
I haven't very many positive comments about the Goodyear Eagle RSA tires that they come with. You can check out
www.tirerack.com for reviews and comments. I ended up buying the new X ice tire for the winter because it just didn't seem like the RSA's would be good in the snow. A friend with a Sunfire had RSA's on his car and told me they are very slippery in the snow so enjoy sliding through the intersection.
Bottom line - it's a Toyota (with a little bit of GM interferance)