I have the paid version I bought last year & just installed on my X a couple days ago. I had become accustomed to the stock Google keyboard & am trying to get used to Swiftkey now. I know they both learn your typing style, so I'm sticking with Swiftkey for a while for it to learn me. Right now, I think I actually like the stock Google keyboard best. Otherwise, the Swiftkey keyboard is functioning fine & I've had no issues with it.
I have used Swype, Swiftkey, t9, and others. I have settled on just using the stock Google keyboard. Works great, very fast and it's just one less app I have to worry about.