I've got a Pugsley on order and have been pondering 1 vs 2 studded tires as well. I rode a few weeks on an MTB with just front studs and didn't find it too bad, though I definitely prefer having both.
I hope 45Nrth was very very optimistic on their estimate of the market for the tire. I have a suspicion I might be riding with zero studded tires if they sell out fast. I've got to nag my LBS to track them down before the weather turns.