I, being very picky when it comes to smartphone keypads, have tried Swype, SlideIT, and Swiftkey X.
I used Swype for 4-5 months (I have had my phone 6 months) and never had any problems with it except right before a new version was rolled out, I got a notice saying that my account had been cancelled or something to that effect. But nothing ever came of it and it upgraded fine.
Not a fan of SlideIT...at all
and I'm currently using Swiftkey since I got it for $.10 at the current app sale. I'm not sure I would prefer swiftkey over Swype if it wasn't for Swiftkey's ability to "learn" words and patterns.