Ive been reading through this a little bit and seems pretty interesting. First of all the average BMW owner will have his car for an approximate 5 years and then sell it to get something new. Even so the cars should last despite the electronics. I have had access to technicians and they have some pretty interesting things to say about reliability in electronics and what not.
1st of all from what I've heard from the techs, the new 3 is rock solid. It has had basically no problems other than curb rash on the wheels (by people like my mom

.........) .
Secondly if the cars have a problem they will eventually get fixed either by a recall or something like that. Im also pretty sure your warranty should cover stuff like that.
(I think someone mentioned there is a big waiting list for M5s but thats not exactly true. I think we have 6 at our store right now, Unless they have all of a sudden sold)