I own a 135i and have a ZCP E92 M3 on order.
I love my 135i, it's a really nimble and fun little car. But when I test drove the M3 it was all she wrote, I had to have one. I'm selling my 135 and my STi and replacing them with my M3.
I bet the 1M is a blast to drive, but I just don't see it being more fun than the M3 overall. It might be more fun on certain tracks, but I spend maybe 4 days a year at best on a track. The other 361 days I'm driving the car around town.
The problem with these debates are that people just regurgitate what magazines say instead of actually having their own opinion based off of actually driving the car in question.
Lap times at tracks you'll never drive shouldnt be the deciding factor on which car you'll buy. Every car I've bought I've fallen in love with on the test drive. One mile in the STi and I was sold. Took the 135 out and bought it that day. I test drove the M3 and fell head over heels. I decided I'd sell both my cars to afford the purchase...and mind you I'm selling two cars I love. That's how crazy I am over the M3.
I've test driven dozens of other cars that did nothing for me. G37, blah. Mustang GT, snooze. If I were to buy into hype though I would've for sure bought a GT mustang because it was as fast as an M3 around some track and it costs half as much. But, speed is not everything, it's about how the spirit and personality of the car appeals to you.