I've had a Fitbit for over a year and have had great success with it. If you preordered a Fitbit and are still waiting, rumor has it you can pick them up at Best Buy. I preordered early through Amazon and received mine, but they are still in backorder if you're just ordering.
In a nutshell, I highly recommend the Fitbit One, though there are some caveats to upgrading if you don't have a Bluetooth-enabled phone. Otherwise, I'd probably recommend going with the Fitbit Ultra as it's still a good buy, IMO.
You can read the full review here: