I think Thumb Keyboard really is the best keyboard on the Android market.
It's just insanely quick to type on, especially in landscape mode and I also set the keyboard height to 80% and it doesn't effect my typing ability but gives more screen estate to the UI I'm actually typing in.
I own both Thumb and SwiftKey X but SwiftKey X has this noticeable lag, it's like it doesn't recognise the next key press instantly like Thumb does.
I believe they're working on multi-touch for SwiftKey X but you have to become a VIP to test out. Not sure what that entails but why they don't just host the APK somewhere that expires after a set date, I don't know. So maybe the lack of multi-touch is what makes it slower than Thumb.
Prefer thumbs speed and layout, but SwiftKey's prediction engine is great.