Love it. I think a lot of the problems users have with this app, is, they think they have to be too "perfect" with the Swypes.
Their accuracy is seriously impressive. To type "Hello, how are you?" I can basically swype my fingers all over the place, sometimes going to wrong letters, and it STILL gets it. You don't have to swype sloooooowly and carefully over each letter in your word. Try it, try being messy with it and watch how it's still accurate. *That's* how it saves you time.
If you're good with asdf jkl; and you can type average or better to average, this keyboard should save you time. Plus it allows normal typing too. So, I leave it on for instances where I want to reply with just my thumb. I can type full sentences holding the phone and swypin with my thumb, not even looking at the phone (because I know where all of the letters are / have been with iOS for such a long time).
This keyboard is miles above SwiftKey as well, IMO. So happy this was added to iOS8.