This is what I attempted when I designed the PalmPilot. The PalmPilot has succeeded because it reliably does what it claims to do, is relatively easy to use, and is relatively inexpensive. Here are some of the rules I use when designing. Often, engineers and designers can't agree on the best way to perform a task. When this happens, their first tendency is to make it an option, allowing both methods.
Good design is like good editing, eliminate the extraneous, leave only the essential.
It is difficult to do. PalmOS doesn't have one. If we found an operation took too much time we either eliminated the feature, redesigned it, or solved the problem a different way so the user doesn't have to wait for common operations. It is better not to do something than to do it poorly. It's tempting to tout all the capabilities of your product, no matter how marginal.