I've been pretty happy with the devices, when they work. But they don't seem built to last. Of the 6 Fitbits I've had in the last 5 years (the original, 2 Fitbit Ultras, 3 Fitbit Zips), only one of them didn't fall apart or otherwise stop working .. and that one I lost. The Zip in particular seems to have an issue with the battery cover, where it wears out and becomes too loose and the device won't stay powered on.