Mine is always off, sometimes or always, it can mess your GP. :|

Having auto attack on is better for new players, but once you get to a certain point it's probably better to turn it off.

Off. It will help you practice a lot in last hitting.

Off because if can easily ruin a hank because ur hero will run straight for he closest enemy which ruins he element of surprise

better off it .. it will lead to fail last hitting creep or unexpected consequence.. for example, centaur damage return will get yourself killed even if you are not hitting and spamming "S"

I have it on, but could try to play with auto attack disabled.

i think auto attack should be off, but im used to play with it since d1, and cant switch to play without it

i would choose off. or else my hero would attack everything in its way..

for me always off - it's annoying as hell if your hero want to rush enemies or creeps to death if you want to buy something or watching other lane

Mine is ON.
Its easier for me to last hit with auto atack - ON, because i last hit with the "S" button.