The biggest problem with autobrightness is, whenever I'm in a room with overhead spotlights, even if they are not that bright, the brightness always goes to 100%. At that point, I have to turn down the brightness manually, and it "learns" this new setting, so the next time I'm in an ACTUAL bright room, the screen is too dim.
Repeat ad-infinatum.
I feel like turning off auto bright but it still more or less works for other conditions so it's a bit of a wash.