I'm still learning the lingo and system, but so far it's fun and a motivator to move more. I haven't reached 10K steps yet, which is the default daily goal. I knocked it down to 5K, and with a bit of effort (actually leaving the house and walking around the block) I've met that for a few days in a row. (Today we went to Walmart and I pushed the cart with one hand so my arm was swinging naturally and those steps would count -- then I paced in the house after supper until the bracelet vibrated and lit up in celebration at 5K.)
I don't have any "friends" in the Fitbit system, and I prefer it that way. As an online writer/blogger I do put some of myself out there, but I definitely don't give away a lot of minutia or anything really private. So the idea of anyone seeing how much I walk (or DON'T walk) in a given day is horrifying. Do your friends have access to your sleep data? Ugh.
I like the sleep tracking feature, although I'm not sure how accurate it is. I had a REALLY hard time falling asleep last night but it still shows me as getting a full 8+ hours. I definitely was laying down and in bed for that long, but I don't know about asleep. It's based on how much your wrist moves, and honestly when I'm laying there reading on my Kindle Fire (another great Xmas present from my mom a couple years back!) my wrist doesn't move much so maybe it thinks I'm sleeping then?
Data is data, and even if it's wrong it's still wrong consistently and I can spot trends.
Do you have a Fitbit or another exercise tracker? Do you like the motivation of other people seeing your stats?