I also have a Model I and am unhappy with the fact that -when last I checked- you can't configure the three or four extra buttons so they're actually buttons. Your only option is for them to generate keypresses, or do mouse-management functions -such as "cycle DPI"-.

This is... frustrating. Multi-button HID devices are -arguably- easier to do than something that pretends to be both a mouse and a keyboard. I get that some games may not understand how to deal with mice that have more than four or five mouse buttons, it'd be quite nice if I had the option to set things up so that I can use them as buttons in games that know how to handle them.