Brightness Sensor not working??

I own an iPhone 3GS. My neighbor just bought one as well. When AIM & Beejive went live with Push Notifications last night, we tested our phone with each other.

Then I noticed that my screen was much brighter than his even though I had set it to about 25-30% brightness with Auto brightness on.

I put both phones on a flat surface, dimmed the lights, and I compared the settings. He was at 50% brightness with Auto on and I was at 25-30% with Auto on, and MINE was brighter.

I can only assume that my ambient light sensor is messed up? Should I take this back to the Apple store and try to replace it? Otherwise it's fine, and I hate having to replace it, but this could be why my battery life isn't as awesome as what I'd expect it to be.

The screen is brighter than I'd like for it to be.

Right now I have it at like 5% brightness to get the same effect as 25%. Ugh.