I've purchased a e46 m3 coupe back in 2004 and haven't had any real issues with it whatsoever. I also owned a e46 330ci prior to that. Thats one good thing about the <e46> M3 is that it can be used for everyday driving. The ride can be a bit harsh and noisy on bad pavement but I hope with the new EDC system for the e92 m3, this can be overcome.
Mines a manual gearbox, and I've found that as the car has got a bit older, and with more miles on the clock the gearbox just seems to be getting better and better all the time.
I use my M3 everyday to get to work, and then at weekends I've got a bike rack on the thing with 3 mountain bikes ! Its good stuff. Gas can be *really* bad though when you've got the bikes on the roof though ;-)
Yes, no regrets about getting the M3, and am looking forward to the new one .... when it finally arrives here next year.