The reason I got my flex 2 was because it was on special for $80AUD ($60.46USD) and it was one of the only trackers in that store around that price range that would track my swimming as well as my steps. I use to be someone that would use free phone apps to record my walks, so I felt that fitbits were just overrated pedometers. I now know how wrong i was.

I don't go swimming that often but it's pretty handy when i do and i tend to push myself more. I'm happy with the purchase as it shows how much i move daily. If you can get it on special under $100 I'd say it's worth it. It's something that will help and encourage you to reach your goals.

I was only doing 3000 steps a day prior to having mine and i had no idea how bad i was, but once i saw how lazy i was it pushed me to become a more active person. I now at least aim for 7000steps on my rest days. I think it's played a large role in me losing almost 40lbs. Even if it only lasted a year it would still have been worth it, but i imagine this will last many years and when I'm down another 70lbs and my bad knees aren't holding all this weight if they have a special on a waterproof one with a heart rate monitor I will most likely get it and start working on being fitter and I might even do a difficult marathon.=)

Not useful - as swimming can't be represented by what the Fitbit would see.

Steps intended to be calculated from walking to give a calorie burn will be all wrong on anything not step based - lifting, cycling, elliptical, stairs, swimming, rowing, ect.

Test your expected calorie burn on this - which is very similar to the database results that Fitbit is using anyway.
Database goes by speed ranges though for calorie burn, so you could be on edge of range about to go into a higher calorie burn - so missing some calories.

This calculator will show you that happening. If it's not off by more than 10% - just use Fitbit's estimate.

http://www.swimmingcalculator.com/swim_calories_calculator.php