Accurate at which part?
To extent I have tried to verify... if you wear it 24/7
steps: overestimated by 5-15%
calories used: very spot on
heart-rate: very accurate
sleep duration: not good, I have Actigraph data to compare with
Sleep cycles: no idea
types of activity (eg run, cycle, min 10 minutes): pretty good
GPS: very good
I've got lots of ppl trying to 'friend' me on Fitbit, it's some kind of scam: "here's my new sports blog" dunno what the scam is, weirdos.