I just helped a friend at work buy an '02 M3, so ask again in a few months
Check the service history with a BMW dealer to make sure it's had the engine recall performed, the inspection #1 and if it has 50-60K miles, the inspection #2 which includes the valve adjustment.
When looking for a car, we drove an '04 330i e46 6 speed and the '02 M3. Even though the 330 was newer and in better condition, it didn't feel as tight as the M3.
Part are quite a bit more, for instance brake rotors are about 4 times the cost of standard e46 rotors.