I barely ever use one finger. Occasionally I will use one thumb, but generally I always use two thumbs.
Well, for me, I usually use two thumbs, but right now I'm using two index fingers, just to try it out,,,
Not too bad, as for when I drive, I have to say one handed with my thumb is the way to go,,,
As for OTHER,, I have used my nose, but only on the ski slopes, and for really REALLY short messages, and only when it's really , REALLY COLD! (and wife's already left couple of voice mails already!
I did learn the two thumb way on the sidekick II, really a great way to type on it,, real buttons to feel, don't need to look at most of the time when you type even,,,