After now owning the m3 for about 2 1/2 weeks and 1500miles of driving (5300 odo total) I find it to be a great car for its appearance, luxury, technology, v8 sound, decent power, and certain handling abilities.
That said as this is my dd I really wish as others have said, that it had more tq, or a nice turbo to propel the car down low. I remember how frustrated I was with to the s2000 before I turbod it, now it's got great usable power down low. Same thing with my wrx after a tune, love the power down low.
That said, I will probably pick up the new one once its released as its supposed to have a turbo. Otherwise, I'm not sure there is another 4 door car that would suite me. I'm kinda been spoiled by my other cars I guess.