I know that some people don't like the idea of having to turn down the screen brightness to save juice on our TB's...but to be honest it is only turned that high in the first place to trick you.
When you calibrate an LCD display for the best picture possible, the first thing you do is turn the brightness WAY down. Brightness is cranked on LCD's when coming out of the factory, so that when you see them in the stores under florescent lights...the brightest one SEEMS best. But having your brightness cranked can actually worsen your picture. (this trick is used on every LCD tv you have ever bought as well).
Now I get it...if you are outside and it is real bright a setting of 20% for screen brightness is not optimal...so you turn it up. But if you want the best picture when surfing, watching videos, playing games etc...and you are not out in the sun...20% is actually going to produce a better reproduction of the intended image/video/game.