To answer your question OP, I brought my 08 e92 M3 used with 5k miles. I too was concerned about buying used, especially a car with the capabilities and driving behavior that the M3 exhibits.
It came down to this:
- I had a good relationship with my local dealer service rep. He did a check for me and told me the car was clean.
- He then told me, that M cars are usually better built cars from their normal brethren, and they can basically take alot of shit thrown at them. As someone mentioned, this M can take revs up to 8000 and just be over-revved to death...its was built to handle this.
- lastly the car came with over 3 yrs of the original warranty left, so I had the comfort to know that any problems (outside of a complete engine blow-out), BMW would take care of the car.
And today, I have over 10k miles on the car and it hasn't caused me 1 issue (knock on wood).
Hope this helps.