Re:no surprise... (Score 1)

There are some studies related to that sort of thing from Georgia Tech's contextual computing group. You're probably most interested in "An Empirical Study of Typing Rates on mini-QWERTY Keyboards," although the Twiddler studies are also interesting since they present a 3x4 button interface much like a normal phone.

The answer to how fast on a mini-qwerty looks to average about 60 wpm, and on a Twiddler the speeds average 47 wpm.

The studies are available at: http://www.cc.gatech.edu/ccg/publications.html