I recently tried out the SwiftKey X app for my LG Android Tablet, and it has quickly become an essential part of my tablet interface. The app breaks out the traditional (cramped) keyboard and moves it into a more 'thumb friendly' interface. Incidentally the app reminds me of the new windows 8 interface they're showing off, and that's a good thing.
It was so intuitive that there was essentially no learning curve. I had to get used to using the same thumb (and hand) for certain letters, retraining it a bit, but it was something that came with ease.
Also a nifty feature was the ability for the app to learn how I typed. This feature is available in a host of ways on different platforms but SwiftKey X adds in a new twist. It can learn how you type via other email services you use (gmail, yahoo). The suggested word function worked beautifully, and even remembered what I had typed in my first email when the program had crashed and I had to rewrite it.
While I haven't tested the app in its android phone form - for tablet owners it's a no brainer.
You can get it for android phones or tablets HERE.