Hi..
Having hands-on experience on a Matrix, I think you shouldnt go for one unless you wish to hold on to it for a long time and have the time and money to attend to the more problem prone MPV than the japanese models.
The problematic areas to my knowledge and experience are the gearbox(on autos), suspension and of course the fuel efficiency. There is an OK 2nd hand market but you will have to bear-up the comments of potential buyers who will condemn the vehicle in all aspects.
Apart from that its an excellent vehicle in terms of looks, legspace, comfort & options (leather seats, cup holders, foldeable rear seats, map reader lights etc) . So, its a bargain. If the Matrix has really won a place in your heart its best you take a Korean Car expert with you and buy one in good condition for a really low price.
Good luck mate!