Once up to speed they are a little more floaty in the corners (Similar to Toyo T1R's IMO), but with the rubber having bigger grooves/cuts to clear standing water this is to be expected.
As for in snow, well they come in to a league of there own, there is just no stopping them even when trying to get it stuck with snow scraping the under tray and purposely stopping....they just grip and go.
Stevo, what tyres are you running? Are they new as winter tyres are supposed to be past there best once they reach 4mm, if that is true or not is another question....ask me in a couple of years
Edit; Stevo, when i bought my 330d from BMW it came fitted with 2 Uniroyal Rainsport's on the rear which caused the traction control light to flicker way to often, almost the problem your having. BMW fitted 2 new tyres, Pilot Sports....problem fixed. Maybe the traction control is over sensitive on the BM's. Are you running the same widths as standard?
Out of the people commenting on winter tyres, who has ran them??