I heard about some people complaining about the notchy 1-2 shift on the older models ('08/'09), but I personally have no experience.
My M3 shifts just fine in all gears. Compared to my previous BMWs, it's one of the easiest to shift. The clutch engagement point is a little too high for my taste, but I got used to it pretty quickly. The clutch also got lighter compared to the older BMWs.
I have no regrets about choosing the MT over the DCT. It really suits the character of the car well IMHO.
BMW CCA Member #xx4477
2006 Z4 M Coupe (e86) 6MT
2013 M3 Coupe (e92) 6MT