taxi, rooms I've been in have been set to just a bit cooler than room temperature - 65-70F. The sterotypical freezing machine room doesn't match my experience. The key is maintaining that temperature when you've filled the room with equipment generating lots of heat - that of course requires air conditioning. Colder is uncomfortable for people and means a higher air conditioning bill, and it doesn't buy you much.
I don't have exact numbers, but it turns out that you want the humidity at the end of the day to be solidly below the dew point (hopefully obvious!) but otherwise reasonably high. This helps to prevent static. I would have thought that humidity is bad, but that's what several sites I've worked in do.
I am sure that there's science here.