A feature from this that might be nice to implement is more than one option available upon long-press of a key, demonstrated here:
[[ http://img836.imageshack.us/img836/7466/device1s.png ]]
This is especially useful in non-predictive T9 mode as it allows long-press and slide to a letter, rather than tapping 4 times.
Edit: Another one from that which I would really appreciate is the ability to swipe to move the cursor by a whole word, not just a letter at a time.
Edit2: Just noticed: I added a word to the dictionary, then tried to write the same word again but with an s at the end, it didn't know what to do. Perhaps the prediction could intelligently add an s or 's to unknown strings which closely match existing dictionary entries, but with an s added. Sorry if that wasn't clear!!
PS Thanks for awesome keyboard!