I prefer anything about 36-37" high. I am about 5'9", so a 37" cutting surface is about 4" below my belly button, and with my arm hanging at my side my elbow is about 7" from the top of the board.
I would say most prep tables and coolers in a pro kitchen aren't quite this tall. Probably around 35" tall plus a thin poly board. So those of you who prefer the board near your bellybutton need to be short or sol.
Sharpening I also like a few inches higher. I usually flip over a half deep third pan and put my stones on that to sharpen, so maybe another 3-4" on top of my counters.