as said in the previous threads of fitness bands, i've had 3 generations of fitbit, the latest fitbit flex is awesome (i've also had other trackers).
one, it's waterpoof, i've lost one fitbit in the wash b4.
two, it's a wearable, as a fake livestrong bracelet
three, long life, of maybe 5 to 7 days
four, pair it with a smartphone and it syncs to that phone almost in real time, no more having to take out the device daily, opening a program and pressing sync.
five, even with that, you can install the included wireless adapter and when you're in range of your intended pc, it will sync.
after more than a year of use, my band is breaking, i'm gonna have to find a replacement, that's about the only negative really.