>>+1 is cold. If you dress right you're okay, except your hands get cold. I don't have heated grips, but if I was planning on doing a lot of cold weather riding I'd be investing.<<
I'd love to get heated grips too, but the big problem is the B4's electrical. I believe it's listed at 250 watts, and most of that is spoken for. I do use a Widder vest when it gets really cold (~-6.6°C), and at 22 watts it doesn't seem to tax the system. I think the vest AND grips (which are typically around 22-35 watts) would be too much for the 'lil bugger.
So far I've had good luck with a combo of TourMaster Elite winter gloves, a set of (relatively thin) motorcycle handlebar mitts my friend brought back from Japan (which are only identified as GWSPORT), and a National Cycle Plexistar II windshield, which gives decent wind protection to the hands:
The only real problem in the cold for me are the levers, they chill your fingers. That's where I'd love to have heated grips. Hopefully I can find an SV650 I've been looking for a while now (a red 2001 model) which will have an electrical system that can handle both the vest and grips. With that and the rest of my cold weather gear setup, I'll probably be good down to ~-9.4°C.