I don't even get the revs up past 2.5K in my neighborhood or any residential type 25 limit area--I had too much grief with my Acura while driving with revs up the at a slow speed. People yelling at me or leaving the little notes on my car. It's just not worth the hassle and the M3 is way more of a target.
I usually drive about 20 MPH as well--I've just had one too many close calls with a kids shooting out from behind a trucks/minivans.
It really pisses people off when about I drive 20 since folks are more or less used to going 35 or 40. I think the fact I'm driving an M3 just rubs it in more. But what are they going to do about it--complain I'm driving "too slow"? No one's bitched to me about it. I'll confess it's fun to slow the "Mom in a hurry talking on her cell while checking herself in the rear view" down. A bit evil? Yeah, but kinda fun.