Cant believe this thread, just spent the weekend looking for E46 M3, trading the GT....interested in your opinion as its my mates M3 that he has had for 5+ years...mmmm....you've got me thinking now.
Well, all I can say is that I can confidently say it will cost more to maintain than 3.2 V6 GT even though I haven't had one.
I remember when I was back in America (yes, I am an American living in the UK lol), my close friend had a 03 M3 coupe SMG. Even SMG is prone to fail much easier than standard manual, SMG was the last thing to worry about. He had a bit of engine oil leak (at 73k miles) and the repair at specialist ran him about $1100 which is around 600 pounds at this exchange rate.
I mean, M3 may not be that unreliable. It's just cost of maintenance which is high and buying a M3 as used (well, it's all used now since E46 is discontinued) is absolutely risky. Most of M3 drivers would want to be in and out of red line quite frequently and hard driving may have worn out parts. I mean, it's really hard to find a E46 M3 under 50k miles as it's been around quite a while, but then, even lower miles may not be good as the car always has to be driven regularly to run properly.
All in all, why won't you opt for 3.2 V6 GT instead(unless you have one already)? I think it will break your heart when it goes wrong but all you need is a fat wallet whilst M3 may have you needed a fat safe full of cash.
ps I am sorry if your opinion is different on E46 M3's. I mean you may be lucky to have a reliable one but all in all, it won't be cheap to maintain regardless!
AND ALL OF THIS WAS BASED ON MY EXPERIENCE AND PERSONAL OPINIONS, so if I am wrong, please understand