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.
Owned this car for almost 10 years, love it almost as much as my family. It stays parked most of the winter, but now that spring has sprung, pop the top and hit the twisties. It handles like a slot car, nothing tracks better. Not the most powerful, but the horsepower race is overrated. Mine is a 5 speed, a 6th cog would be nice, but NEVER would I consider a self-shifter. Car is all smiles :-) Even 12 years old I still find people gathering around it in parking lots.
I just purchased this car in Sept. of 2005 and I love it. It really does handle well (can't seem to squawk the tires no matter what I try). It's a real headturner and you get a lotta people saying "Nice Car". I get about 27 MPG on the highway (not bad). Not a cushy ride so you'll feel the bumps but plenty comfortable. Seems like the best torque is at mid-range (30-60 MPH). The brakes are impressive (you stop like 'right now'). No leakage with the ragtop at all. Harmen/Cardon sounds great. Yes, you can get groceries with it too. I even get two sets of golf clubs in the trunk. No problems as of now.
This is a well engineered car that is a blast to drive. The car is balanced and poised on either back roads or the highway. Maintenance costs can be high, but this is the trade off for owning a great sports car. My M is ten years old and still handles and drives better than many new cars. The convertible may not be for everyone, but I love the top down cruising. Find one that has been taken care of and you will not regret it.