I bought a used M3 after shopping it against the 328 and 330. All of them do 0-60 pretty quickly, but after 60 only the M3 keeps on going, going, going. This car almost never fails to put a smile on my face. It looks great, handles smartly, and accelerates quickly. Drop the top and crank the tunes, and life doesn't get much finer. The back seat makes it a fairly practical car -- it'll carry 4 adults in a pinch, or 2 adults plus a week's worth of bags. It won't carry a family of 5, tow a boat, or haul sheets of plywood home from the hardware store, but it does just about everything else.
M acceleration, M handling, M braking, heated leather seats. The hedonism of ripping along at outrageous speeds with the top down and A/C blasting on 100 degree days. Stability control is subtle, effective, and can be switched off for tail-wagging fun. Gets 25 mpg highway even with a lead foot.
6th gear for cruising, more power, slightly roomier rear seats. Got more money? The e46 M3 ('01-06) has these.