Personally. I got really used to it on the DX. I caught on quickly, and was pretty good at using it. It was especially helpful if you only had one free hand (ie when driving as bad as that sounds or doing other things... )
Anywho, after a while however I got really fed up with the word prediction choosing the wrong word or just the software messing up. I switched back to the multi touch keyboard so that if a mistake was make I could blame it on user error and not the phone. It was a psychological thing so I wouldnt get mad at my phone. haha. Anyway, I'm getting used to / better with the stock keyboard.
I tried 8pen for a while and just gave up. the learning curve was waaaaaay to steep.