I worry that this will be the biggest obstacle for 8pen to overcome. I'm planning on trying it out, for sure. I think the learning curve will be steep, but if you can delay gratification it'll be a pretty nifty tool.
I agree that a tutorial would be useful, and that's exactly the problem.
From trial and error, people build up gazillion mental models of how certain things work. When I show you a bottle of red wine, you most likely know by glancing at it, how the bottle can be opened. That is because you've built up a mental model of bottle mechanics as well as different type of bottle caps and can map them to the new problem space (new unseen bottle).
When inventing something new, especially something as basic and "known" as an input method, you can greatly ease adoption by relying on existing mental models of things people already know, then map your new interface to that.
Swype would probably work reasonably well without displaying the underlying keyboard, but I assume they do so to guide the mapping process.
Recently acquired BlindType does the same. I remember that they even state somewhere on their website, that the typing works without displaying a keyboard at all. Unfortunately the site is down after the google acquisition, but this youtube video illustrates the "typing without keyboard": http://www.youtube.com/watch?v=m6eKm1gUnTE (skip forward to 1:02)
