The fatbike forums on other message boards are full of posts extolling low tire pressures -- people saying they are running 5 to 7 lbs. My pump may not be very accurate (I've ordered a 1-30 lb presta pressure gauge to be sure) but at an indicated 12 lbs, I find the pedaling effort to be enormous. Pumped to an indicated 20 lbs (the max that the tire recommends) I find that the bike rides great. I'm mostly on paths and packed single track without much in the way of deep snow or steep off-road hills (so max traction or float is not a goal). When I get the new gauge later this week (hopefully) I'll be doing some similar tests to find the optimal tire pressure for the kind of riding I do.