I've been on the trainer once this week, for just 30 minutes. Since I haven't been on a bike at all for almost 4 weeks for various reasons, it was uncomfortable.
I've put the studded tires on my commuter, but can't get motivated to actually ride it. For some reason, walking the 4.5 k to work seems like less hassle, even if it does take longer. It's more exercise, certainly. Actually, if you add the time I'd have to shower after riding in - I can't avoid sweating on winter rides no matter how carefully I choose the clothing - it probably doesn't take that much longer.