Just to second (or third) the interest. I love Balsamiq, but we are running into the same issue. We unfortunately aren't comfortable showing potential investors the prototype directly on iPhone due to the resolution issues so we are potentially going to have to re-mock them in another tool. So it's pretty significant friction. The text on the letters of the keyboard is even hard to read.
I'd love to get involved with the beta too.
Sorry, this isn't meant as a gripe, just reinforcing that it's definitely a top interest for us as well.
Thanks, keep up the great work!