After reading many members' post about how their car basically sucks in the snow, I say with a good set of winter rubber the E90 can hold its own. Case in point:
As part of a trip I did a couple of weeks ago, I also stopped in at the Nürburgring hoping to get a couple of laps in. Unfortunately the track was closed because of all the snow (really sucked!).
However, I went a bit further to the experience world and nearby they had this closed in bit that hadn't been cleared of snow. There were a couple of cars sliding around there so I waited until they left and I could have the whole space to myself to test the E90 with the new snow tyres I had put on the day before (Blizzak LM-22 RFT). I tried all 3 DSC modes (On, DTC On, and Off).
On: The car wouldn't let me slide at all. I did a full lock turn and it was coasting (I couldn't accelerate, but I was moving). Then I was driving around at about 30-40 km/h (20-25 mph) with ease. The circle I was driving was maybe only about 15-20m radius, if that. DSC only engaged when I tried to change direction too quick, was too aggresive on the throttle, or going too fast. But when it did, it made the car do what I intended. No surprises or "oh, shit's!".
DTC On, DSC Restricted: Starting to get fun. The wheels would spin on take off, but only if I punched the gas (remember, my car has more torque than a 330i at 340Nm or 251 lb-ft @ 2000 rpm). On quick direction changes, the car would slide a little, but DSC still kicked in to make sure the car didn't go too wide and that I moved more or less in the direction I intended (give or take a few degrees). Not recommended for snow driving because the car does slide around, and when DSC does kick in it's a bit of jolt.
DSC Off: The only thing still on is the ABS. This was the most fun of all, but only in a 'controlled' environment. I wouldn't dream of turning it off on a public road. The tail end would kick out under power, I could do 180's with ease, and yet it was still driveable (althought there were a couple of "oops" moments where I pushed the envelope too far). On the whole though, with controlled throttle movements and steering inputs the car was very controllable. Playing in the snow with DSC off is just about the best fun you can have with your clothes on!
I recommend that everyone finds an empty parking lot and gives it a go. Not only because it's a heap of fun, but I found it to be an extremely useful learning experience. The car told me what it can and can't do.
Unfortunately in my excitement I didn't get any video. You'll just have to make do with a couple of pics.