Currently running all season 225/45R18 Bridgestone Potenza RE970AS Pole Position on a F30 335i xDrive. It performs relatively well in dry cold road conditions. The handling in wet road conditions is not as good as the summer tires. The handling capability in snow is just sub-standard. Generally disappointed with the overall winter handling capabilities. Definitely would not recommend these tires for anyone who encounters snow during the winter season. It handles poorly in an all wheel xDrive much less on a two wheel drive. I would sell it if I though I could get anything reasonable for it. That's not likely so unfortunately I'll have to live with it for another 50,000 miles or so.
I know this OP will get inundated with the virtues of winter snow tires. But before I'm tarred and feathered, let me just say that my experience with a Lexus RX300 with all season tires (albiet a different type of tires) has been nothing but phenomenal. It is nearly bullet proof. It has to be pushed to extreme limits before reaching its threshold.
I will definitely get winter snow tires next time when opportunity permits.
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Update 2 Jun 2013:
Just completed a road trip through Grossglockner High Alpine Road in Austria.
I google searched multiple reviews giving this RE970AS rave reviews about how good the tire performs. I gotta say that I am disillusioned with the overall performance of these tires. During periods of moderate to heavy rains, the tires were hydroplaning like it was going out of style. This on an AWD F30 335i??? Other lesser cars were flying by without any hydroplaning problems. It performs poorly on snow and wet conditions. The only time it performs moderately well is under perfect dry and warm conditions. I've been driving for over 20 years and have never experienced tires this bad. I on the verge of getting rid of these tires to get a new set. Very disappointed and a waste of money.
Ciao.