There are issues with everything bro.. 335's have HPFP gremlins and are notorious for going limp and the turbo's are $$$.. which is why I avoided that to go with an N/A N52 motor..... lo and behold.. issues (granted I do track my car)..
Because my engine is magnesium/aluminum (lightest 6 cyl ever produced.. ohyeah!) they had to use aluminum bolts (some chemical reaction crap).. which are now broken and stuck inside and the motor is leaking oil from the valve cover gasket... only when I looked it up did I realize that this is as common to N52's as HPFP failures are to 335's..
Do I regret owning the car because of this shit?? No.. because when you're complaining that your car's broken.. remember that you're complaining that your mag/alum BMW motor is spilling oil cus its so #%&ing badass.