From UI perspective I think that there should be at least two interface models. One for simple "do one thing well" type of programs, and other for complex programs like spreadsheet. The simple one could be optimised for use without stylus, and the other one with stylus in mind. If a program doesn't fit well in either category, it could have both interfaces with some features hidden in the simple version. That way the interface wouldn't have to compromise between these two worlds.

Oh, and I'm definitely for the right hand hardkeys. They would enable gaming on a totally different level, but could be programmed to bunch of things in regular programs too.