I have had an SMG M3 since I picked it up new at the performance center in April 2002. No problems.
I have several friends with SMG M3s that also have had no problems. Yes, if you have major problems, it can be expensive to fix, but IMO, there are plenty running that have never had issues.
The actual tranmission is the same as the manual.
'95 Alpine M3 LTW
'00 Dakar M Roadster
'02 Topaz M3
Red/White SRF #4 (Chassis 561)