I use inverted on fps games, but normal on 3ps.
I rationalize my fps controls with the idea that the muscles in the back of your neck contract to make your head look up and vice-versa.
my friend was totally confused when trying to play MGS4 with my controls. Up is up in 3p mode, but up is down in fps mode... kinda confuses me talking about it, BUT IT WORKS DAMNIT!