I'm afraid that I probably know the answer to this one, but I might as well give it a try:
Is there a way to configure extra mousebuttons (button 4, 5, 6 etc) into keystrokes using the base OS or a free utility?
Some background: I've used USB Overdrive since forever, both to do this and to control gamepads. Today I got a Magic trackpad - simply because I wanted to play with it, and it was cheap enough. USB Overdrive is incompatible with the Magic Trackpad - as in, nothing beyond basic mousing and clicking works, even if it is disabled in the settings. For this reason I had to uninstall USB Overdrive, and so I lost custom button config.
My requirements are pretty basic - I'd like to configure enter to the big thumb button and esc to the small one on my Logitech MX 510. I've used this function since forever, and I'd like to keep doing so. Options that I'm aware of:
* Steermouse. Highly regarded, but fairly expensive for what I need it to do - especially if USB Overdrive is updated at some point.
* The Logitech Control Center. This has a terrible reputation. Does anyone know if it has improved? Does it still use haxies?
Is there anything else?