From what i've been reading it seems like the e90 330 is a pretty reliable car. It's the 335 that has all the major issues with the hpfp. I've owned a e46 325 and now own a e90 330. Theyre both nice cars but imo the 330 is quite a bit nicer. Drive one for yourself and see but I wouldnt be too scared of it ... a 335 I would be.
Just make sure you check it out like you would any used cars maintence records, accidents etc ...
Check e90post theres alot of great info on there.