I use my pebble everyday. Battery is about 4 days or so maybe 5. Its extremely useful for me, it stops me from having to look at my phone all the time. Check emails and texts and I can decide whether I need to respond immediately or later. Biking riding I can control my music and with android tasker I can activate a slew of task on my phone remotelythe battery life is doo-doo and the functionality is incredibly overrated.
Honestly, if nike came out with something on par with this, i'd get it cause it only seems useful as a workout device.