I purchased my CPO 2009 BMW 335d with 46k miles about 3 months ago. These are the things that the dealership had to do to it so far:
1.) Replace the cyclinder head (leaking fuel injectors)
2.) Replace the intake and outtake vales
3.) Replace all six fuel injectors
4.) Replace fuel pressure sensor
5.) Replace mass air flow sensor
6.) Replace drivers door panel (gap between panel and armrest)
7.) Replace drivers door control panel (paint peeling)
I get about 36 MPG, mostly highway with some city driving. I love my car, even with all the problems I had with it. It's fun to drive and you can't beat the power/torque with the great MPG.
What I like about it is that it's a CPO, which covers all the major issues for a total of 6 years or 100k miles, which is the reason why I bought it. I was specifically looking for a CPO, otherwise, I would never get it.