I'm very, very happy/impressed with the Bilstein B4S / Eibach pro kit set up I have on my F31 touring (same engine as your 328d IIRC)
fongpei 
They've been on the car since beginning of Jan; have covered c1k miles now
Handling is superb; they're firm, but not M Sport firm (as in not crashy/jarring at all); they allow the car to take rough roads much better than the OEM M Sport suspension; but they also allow the car to handle much better and take bends/roundabouts much, much better etc
They were fitted alongside a full suspension overhaul; so that does make a huge difference
I've not run Koni shocks on any recent BMWs; but I did fit them to an E46 quite a few years back and my first E39 after that too and had constant issues with them (leaks mainly etc) and that put me off them a lot
I've also known quite a few folk with similar issues here in the UK and some quite recently