Are you thinking all seasons only or summer rubber plus A/S for winter?
A dedicated wheelset with performance winter tires is really the way to go. I have the same amount of confidence in the handling of my car year round and it's crazy fun to blast through the rain and some snow with sure grip.
If you want to switch completely to A/S, there are some decent options out there that can do everything but don't accel at anything in particular. The new Michelin Pilot Sport A/S 3 will likely be a real gem. http://www.bmwcca.org/node/5047