I recently purchased a Sony Clie handheld computer for the purpose of using it with Gerald Perry's Exbal ballistic program. Because of the excellent reviews from many people here, I decided to try it. I'm glad I did. The ability to calculate real time data in such a small, portable package is quite amazing.
For $99., the Sony Clie was a quite a deal, with 16megs of RAM. That's a good deal more computing power than my first desktop. I've played with ballistics programs for years, starting back when they were old DOS programs. Exbal is top notch in my book!