I have had a 1998 Mitsubishi Galant for over 3 years (103k miles) and can't wait to get rid of it. Although I have had very little mechanical problems, there have been quite a few cosmetic and other problems:
1) Major paint problem. I have little paint left on the room, trunk, qtr panels and its starting to come off the hood and doors. I know have a white haze. I waxed the car when I first bought it (used in Nov 00 with 43k miles) but once the paint problem developed I stopped. It is a problem on a lot of 97-98 black galants. I have even seen it on newer Galants. Mitsubishi denies responsibility.
2) FM radio stopped working on stock deck with about 95k miles.
3) radio antenna won't go down.
4) Lots of creeks and rattles in car.
5) Resale value is in the toilet. One of the worse resale values manufacturers on the market.
6) Engine knocks quite a bit! Lots of noise coming from the engine. I have heard of people replacing the transmissions several times on there galant. My dad's 99 camry is silent at 123k miles. Still sounds brand new.
I know there are other problems, but these are just a few. The car is 6 years old, but the paint and problems on my mom's 275k mile 92 Corolla are far less than my Galant.
Needless to say, my next car will be between the Corolla and Mazda 3. I am not at all concerned with the quality of Mazda. I think they are great cars. I am going to test drive both cars tomorrow. I will NEVER buy another mitsubishi again. My brother has a 98 Eclipse, the sunroof leaks!
Good luck with your decision. Stay away from Mitsubishi!