The only complaint I have (or at least can think of right now) is that the directional pad is too small and awkwardly-shaped, being that the Up & Down keys are way too skinny. I always hit OK by accident.
Other than that, I can't get enough of it. I'm writing this from my i730 now.
Yeah, just go to Start then settings. Then buttons, then Button 1. It's the first button. It has a picture of a tape next to it. Highlight it then go to the drop down menu. Select . Then go down a little farther until you get to Button 1 Long press. Highlight and select Record (or any other option) and tap ok.
This is for Windows Mobile 5, so if you are running 2003 SE, it may vary slightly.