I have the FWD 1.8T with ASR and EDL and took it for a three day trip on snowy/icy roads around Mammoth Lakes CA this week. WOW! I have very worn Potenza 960s with no sipping left and the car worked great. I was pushing it a bit to get a feel for how the car would perform (new car for me) and found the limits were MUCH higher than with my old Civic with new M+S tires.
Snowy roads: Almost no slip on flat-ish roads under accel or around corners at posted speed limits, even under moderate breaking or accel. Lateral grip was impressive.
Icy roads: Good accel under most conditions. Under hard accel the ASR light would blink but always kept me moving forward. Some noticable problems while starting up steep icy hills from a dead stop, but remember my car has bald tires. Under breaking the car stopped well as long as I stayed out of the ABS. Once the pedal starts to vibrate traction gets terrible; probably loses 30% traction under ABS.
I'm planning on putting on a set of 4 Continental ExtremeWinterContacts as soon as I can afford them. Once they're on, I'm certain the Passat wagon will get us up the hill in any conditions the roads are still open, assuming my heater core doesn't re-clog.
Another point worth mentioning is we saw dozens of A4 and Passat FWD wagons in Mammoth. It's a go-to snow car here and everyone loves them in the winter mountains with proper tires.
So in conclusion, even though I have a 4x4, after our test spin, I will only take it if the roads are R3 (4x4 + chains required). Otherwise, the Passat is coming.
-g