Two friends of mine recently bought an M3 each, and they are worlds apart. One is in carbon black, the other in red. The red one was spotless inside and out and cost £16k, whereas the black one is not as tidy and cost £15,500, both in convertible guise. Nice cars, but as with anything else, lemons are definately out there and these can cost a fortune to sort out.
The black one has had a few major issues already - the rear coil springs snapped in the cold winter, a coolant pipe burst and dumped all the coolant, the battery failed after a couple of months and it turned out the garage had fitted an incorrect battery just to get it off their hands (apparently the proper ones are a lot of money), the multichanger doesn't work and cylinder no.5 has recently flamed-out. They think its a faulty coil pack IIRC, but not sure if theyve fixed it yet. The bodywork isn't in great condition and has chips and dings in quite few places.
All in all, I'd be pretty miffed if I'd spent that money and ended up with a complete load of toss. I don't think he really thought it through to be honest - he is 22yrs old (same as me) and paid £3k on insurance for the year (I pay £520 on my CTR). Tyres cost an absolute fortune let alone tax and fuel costs. Secretly I think he is regretting it now, but he has little choice but to stick with it as he still has over 4 years finance to pay on it! Ouch.