I've had pretty much every common issue with the 3.0 engine.

Short list that I remember off the top of my head:

-Back bumper had to be replaced because of defective brackets holding it up. You can see ripples in the bumper when looking at it from the back
-Rear brake light housing had to be replaced because of water in them. BMW has now upgraded the materials used to seal the light housing better
-Plastic radiator cracked. Well known issue
-Water pump died. Well known issue around every 60k miles
-Rear suspension air bags died. I consider this just routine maintenance. You can see if the car is "sagging" when parked which will tell you if the bags have deflated.

I'm sure there are more, but I don't remember them off of the top of my head