For anyone that hasn't ridden a fatbike: It is much like riding a suspended bike. At 7-10 PSI, the tires soak up roots as well as any FS bike, and they float on top of sand, mud and snow. They don't accelerate as quickly, and taking quick/last second turns is tougher than on smaller tires. But the ability to ride up and down sandy/muddy banks and through swamp trails is a huge benefit.
these Origin8 4" tires float pretty well, and have 120 TPI (the best thread count available) but I am curious about the larger ones. I might try some 4.8"s in the future.