I bought my 2004 mazda3 used in 2006 with about 30k miles. Water pump died at 60k, alternator fried at 80k. Transmission crumped at 120k (ouch!). Fun to drive, surprisingly smooth on the highway for a 4-cylinder, and a good looking car inside and out. I'd buy another one, but probably opt for a 5-speed next time.
Sporty performance and appearance, leather interior, nice overall design and ergonomics.
Brakes seemed to require a little more attention than usual. Tiptronic automatic transmission has potential reliability issues. Get a 5-speed if you can.