Those people arguing for handwriting recognition being so much more superior than this need to seriously try to consider, one, how easy it is to get properly recognizable characters out from thumb movements. (Anything other than a thumb, and you need two hands to do it, and that's already a disadvantage to a large chunk of the population.)

Secondly, I feel that everyone arguing for this being an inefficient and/or complicated method, as, simply put, stupidly not thinking beyond their own current predispositions. It's like arguing that keyboards with letters 'randomly' scattered about (hint, qwerty and similar layouts) are inefficient. Do you really think that there weren't thousands of people complaining about stuff like keyboards back when computers (and before that, typewriters" were coming out?

I just find it utterly lacking in ability to see beyond one's own ingrown behavioral and cognitive predispositions. Do I think it would be a horrible pain in the *** to learn to type with something like 8pen? Especially after I already learned handwriting, regular typing, and T9 typing in the years when my brain was more flexible? Yeah. But I can also realize the wonderful efficiency of something like this. It's really only barely more complicated to learn than handwriting in the first place, and definitely no more complicated than typing on a computer.

It's different, and that's why people seem to keep objecting to it as much. But it's definitely not bad, and it's not less intuitive to learn than T9 or typing - and if you just imagine how the process would flow together you realize that it's a lot safer than handwriting recognition and button-on-touch-screen methods - because you can feel approximate fourths of a rotation a lot easier than you can feel distance between letters on a perfectly smooth screen. And with handwriting input, you can barely use it one handed, and while something like graffiti's input method seems rather nice, the actual speed of writing every letter, I suspect, ultimately becomes faster on the 8pen/Qwo input methods than with graffiti. Since you have to lift your hand every time you write a letter, while with a good enough touch screen, this letter-wheel input method type allows for constant hand movement.

Don't forget MessagEase.

Similar idea, except gestures don't connect up like with 8pen. (Still has the potential to be much faster than the usual 3.5" touchscreen keyboard!)

For kicks, I blind-typed this entire message with it on my iPod Touch. Perhaps needless to say, the dedicated hardware keyboard is still king!

I'm not too bothered by touchscreen keyboards because I tend to find it quicker to stop for a moment and use the keyboard. But anyway, to see how difficult it was to write I opened up the sketch app on my N900, and proceeded to write one handed with my thumb, and it wasn't difficult at all, so something like Graffiti* which uses slightly modified handwriting should work quite well one handed with a thumb.

The reason I wouldn't want to learn something like 8pen is that it'd take far too long to learn for the little use it'd get whereas something like Graffiti would be very quick to learn since it is based on regular handwriting. When learning something new that will take up a substantial amount of time to learn you have to consider what benefits there are to you and if it is actually worth the time investment. For people who write lots on a touchscreen only device 8pen may well be worth learning, for most people it won't. For me, I'd be happy with a decent T9 implementation on the N900 for short messages, and the keyboard for longer ones.

*Graffiti is now available for free on Android for those are interested and didn't already know.