Here is something pretty cool that I stumbled upon while typing an email on the Treo 700P (Palm OS version). If you hit on the option key (the little black square on the bottom left) and then menu key (far bottom right) the screen and keyboard back light will automatically dim to it’s lowest readable setting. Not only is this fast and easy when you need to check your Treo in the dark, like in a boring Powerpoint or when you get a 2 in morning message; but it’s also a great power saver when you’re Hotsync’ing over Bluetooth and you’re now running into the 5th minute of the Hotsync because you set it to back up the videos of your kid’s swim meet. Just dim the screen instead of fiddling with the brightness. Next time you hit power the power button you’re original brightness setting will return.
UPDATE: The quick dimmer shortcut also works on the Treo 650. Still no idea if the Windows version has something similar.