Both DW and I have the Fitbit. We are both on our second. I lost my first one that I had clipped to the pocket of a business shirt. It just slipped right off, I guess when I pulled my passport out of my pocket, and I didn't notice. I bought a second and I clip it on the collar of my t-shirt, under my business shirt now, and sync/charge it once daily.
DW's first one died after about 2 months. We got her a new one under warranty. It worked for about 3 weeks and now it seems to have died. We won't be getting another one. We both like them...when they work. But only 2-3 months of use means more than a dollar a day to count yours steps!!!
I've also got a Nike+ FuelBand. I would recommend that for the younger folks, but It is a little bigger and bulkier than I had anticipated, and I have a bit of an issue wearing it all day when I'm working (doesn't go well with a business suit...another reason to FIRE