Or you could so what I used to do..cancel your current contract...go to the other carrier..Put your phone on Swappa or Ebay, and use that money to pay off the ETF
If you are the type that always wants the latest, then the phone wont last 6 months, if you are the type that just wants a working phone then it will last as long as you want it too.
I've been happy with the software updates on my S3 so far. I like the look of the HTC One. Let's hope they give the One decent support over the next 18 months at least. ;-)