I find that a very large fraction of the typing I do while programming is not code entry. An amazing number of keystrokes go to navigating between and within files and directories, running tests, and looking up documentation. A good example of this is debugging -- it's possible to spend hours debugging without entering much code at all.
This also assumes that you'll use your greater productivity per character typed to type less, rather than just maintaining your typing at the same level, and increasing your productivity. Changing your habits is possibly more essential with RSI than changing your tools.
pg: I disagree -- I still find it puzzling that you made this design decision about Arc. I program mostly in Common Lisp and I use very few keystrokes. SLIME+paredit+redshank in Emacs allow me to do structured code manipulation with impressive dynamic completion (as in m-v-b<TAB> -> multiple-value-bind).
In spite of my RSI problems I don't feel a need for more succinct naming. Succinct languages, yes, abbreviated names, no.
I mean this quite seriously. I've consciously tried to make Arc easy to type.