You wouldn't know it to look at me, but I love my Fitbit. I have the Force; the one that was recalled because there was nickel in some of the parts that touched the skin which caused an allergic reaction for some users. I haven't had any kind of reaction so I'm still using mine. My girlfriend had the Force as well, but the rubber near the display lifted up (as if an adhesive had let go). Fitbit couldn't replace her unit but instead gave her a refund, and she had to choose another model.
Fitbit makes the Flex, which is also worn on the wrist, but it doesn't track "Stairs climbed" (an important measurement in our hilly neighborhood) so she settled on the Fitbit One which clips on. It's not a big deal for her since she clips it onto her bra in the morning and forgets about it, but when I had a clip-on Fitbit I was continually forgetting to move it when I changed clothes.
The point I'm trying to make is that there's currently a gap in the Fitbit line where the Force used to be; they need a full featured activity tracker that you wear on your wrist.
The new Fitbit models are (assuming the leaks are legit) the Fitbit Charge and the Fitbit Charge HR. The Charge seems like a pretty direct replacement for the Force; it tracks the same things including steps climbed. The HR model adds heart rate tracking via something called PurePulse, a feature Fitbit hasn't offered until now.
Presumably Fitbit has figured out how to make the Charge with no exposed nickel or anything else that could cause a skin reaction. Personally I hope they've designed in some kind of cover for the charging jack; I've found that the jack can get fouled with gunk if you're doing a lot of dirty outside jobs while wearing the Force (dirt gets trapped between the band and your skin and eventually finds its way into the charging jack).
Again, Fitbit hasn't officially announced the new models yet, but they'll probably do so soon, so if you're shopping for an activity tracker it might make sense to wait a few weeks to see what kind of pricing Fitbit offers on the Charge and Charge HR.