I tested the 8pen app - I am not sure I would be able to memorize it, beside it was buggy and did not work for me in many cases.
I tested SlideIt and I found it fast when it works, but correcting words that were mistaken takes too much time, some words I tried many times and failed. Space bar gets in my way very often.
Finally, surprise, surprise I tried VOICE dictation and it works like a charm! Yes, I have to think about what I will say, for best result the whole passage ahead of time, then I have to say it properly, but it gives me a super-fast, almost 100% correct results.
I will try to continue with voice dictation whenever I can. I think the input device of the future will be couple of buttons:
1) microphone dictation
3) pointing arrows because doing it precisely with finger is very hard on small screen