I don't know if anyone else has noticed it but I have seen that if you have the screen brightness doesn't stay the same.
If you turn the brightness all the way down, turn the screen off and then back on it is brighter then it was to begin with. You can go back and click the power brightness button again and it "gets brighter" (actually dims the phone).
It bugs me a little bit but not enough to really worry about it. Has anyone else had this issue? or know how to fix it?