Most of the issues are to do with the same N54 engine that's in the 135i and the 335i. N52 engines in the 125i and 325i seem pretty solid as far as I know.
Recalls for non engine related issues in our E82/88's are mainly related to the rear tail lights. I'm assuming that the car you are looking at is a pre-LCI model as it's already out of warranty.
The pre-LCI tail light has issues with the LED tubes going out and the third brake light has issues with cracking. Both were issues replaceable under warranty so the car your looking at may already have had that done.
Apart from those I can't think of anything else on the top of my head.
Edit: I forgot to say, good luck with your purchase