I have one of the originals. It's useful if you do low-level programming a lot, and in a pinch you can also use it as a standard calculator. The biggest limitation is that the screen can only show 8 digits. In binary mode, this can be awkward if you're working with variables that are more than 8 bits. The calculator has functionality for scrolling around the number that's being displayed to try to work around this, but it's still a little annoying compared to newer calculator designs that can show more digits at once.