"Fitbit only usable device, Nike Fuelband total shit".
I think they're all quite usable. In this space utility is not dependent on accuracy, for most people, because for most people it really doesn't matter if you get an extremely accurate step count. What matters is that you get a reasonable estimate of your activity level, as compared with you activity level measured on other days.
You could argue that something that sometimes only registers half the steps might make you fitter .... if you exercise until it says 10,000 steps every day you could be doing a lot more.