I agree with laminationman...
...it's too fast, especially to start. Plus the letter-swapping can seem a little random. Many times I'd try to set myself up for a 5-or-more letter word, only to have the other letters move around when I tried to move in the last one -- and I'd end up with another lousy four-letter word...
If the interface was a easier to control, you'd rate a higher score from me. But I grade tough.