All the bmw "S" derived engines have problems with bearing spin
Many bmw M owners look at them as a servicable item now.. god knows why, no other manufacturer seems to suffer the problems bmw do..
Like you say, the M3 is a great thing on the track and if that's where you spend most of your time then I can't think of a better car, they have a great chassis ... power and torque wise they are down on all other cars in their class... the 400 bhp claimed is well around the rpm range, totally unusable on the road and makes for a confusing, frustrating experience...
As you can tell I'm not a fan, and I have had previous generations M3's and adored them... to me the E9x was just a letdown..
Like you say, coming from a 996 you will be well used to that bum clench every morning as you twist the key