There is a trade between complexity and efficiency. You can cram information, shortcuts, and tricks (eg: the vi editor), but it requires a mental switch, unless you really really have been used that particular application.
I think one goal of Apple is to free yourself from that switch. Making each application UI a no brainer, you can concentrate on your job, and not in UI interaction. I think that's where most of the love for the iPhone comes from.
You should consider that an iPhone application is designed to be used with your fingers, and then ponder if designing for a stylus would improve it as much as to make it worth it.