I've gone for 18" staggered sizes (225/40 and 255/35) Falken HS439s on style-189s, refurbed in anthracite. Yet to fit them though.
I ran Kuhmo KW27s in 225/50/16 on my Z4 for the last few winters - rate that as OK but not spectacular - grip in the wet wasn't the best but I put that down to the narrower width hence compromising this year with 255 rears on my 330i.
Nankang SV-2s: got them on my campervan lol. Not the best winter tyre but far from the worst. Towed the wife's stranded car out of a snow drift a couple of years ago (before she got winters for hers) without a problem. Get good ratings from Merc forums too.
Only other winter tyre I've used is Falken KW23s on the wife's Fabia vRS and again they're OK - not as good as the KW27s I had though IMO.
BMW e90 330i M Sport