[Fondueset]

We do 5 mils here down to 3c. A nice add-on is a little 1.5mil vest under the suit - extends dive times a little without too much bulk. We also sometimes use henderson ice masks - these add quite a bit of warmth (its amazing how much heat loss there is through your face) but I've gotten away from them lately because they insulate you from the environment so much.
Anyway - another helpful hit - in cold weather suits that are smooth neoprene on the outside are much warmer - because of the reduced heat loss to the air during breathe-ups. The difference is pretty dramatic thought he suits are much more fragile and I still think nylon out is best for a general purpose suit.