There is a long thread about them on MTBR. They are geared too high to ride trails stock, besides they difficulty of trail riding without a front brake. If you lower they gearing so you can get some torque, the first thing to fail will be the rear hub, the second will be the bottom bracket. If you are handy with a torch, canti studs can be brazed on allowing you to run a set of pugsley wheels that will cost twice what you originally payed for the bike.
If you are getting one for occasional laughs, go for it, but don't expect it to do what a Fatbike is designed to do.