There is a light sensor to the left of the earpiece that automatically dims and brightens. Test it out. Cover the speaker with your finger, it will dim. Shine a light into it, and it gets bright. I think it's great!
I installed a program called Lumos (
http://www.freewarepocketpc.net/ppc-download-lumos.html). This is an advanced manager for the light sensor. I've attached the cab file if you want to download it.
Merry Christmas!