I use auto_win pretty damn often. I only fight battles myself when...

-I'm uncertain if I would win or not.
-Big armies involved.
-A decisive/Strategic Battle
-I feel like it

Other than that, I auto_win everything. It just becomes too boring to play the game, when every turn you fight the same stupid stacks compromising of a few units. If it wasn't for Auto_win, I would probably quit the game altogether until EBII.