Hi Ze Tropa,
I have had the Steam Controller for about 9 months now and been playing A3 and many other games with it for all that time, on a daily basis.
Though I do use the keyboard for some A3 activities, I almost exclusively use the controller and the usability, freedom and controll it affords is excelllent.
Get the Armagerd profile off steam for it too. Free and may take a little to learn but has every binding you are ever going to need for infantry or vehicle.