Now that more of us have our devices, I think this app has become more relevant to our discussion. It basically allows you to calibrate the autobrightness setting to your personal preferences.
Using it to avoid unnecessarily bright screens should help with battery life, and might help with the burn in issue.
Setting it to appear in the notifications bar it shows the current ambient light in lux, and your screen brightness. Clicking on the status allows you to adjust the brightness and if you click the "link" icon, it will be added to your profile. Included is my current profile. I've only got a few links because I did a reset yesterday and haven't been outside today......
The app also has a day/night mode that warms the screen in evening hours (supposed to help with having the blue/white light interfere with your sleep schedule.