Are there any plans to add gamepad / controller support in the future? I like to play games using controller since it can make for a more relaxing experience and I think that the game could really benefit from implementing some sort of support for gamepad.

With the amount of clicking, dragging, holding keys on the keyboard, typing, mouse wheel.....I am going to say not likely on this.

I might be saying this for no reason, because this was said a while ago, but there is hope for controller in the future. As of 0.8 I've seen some hints to it, like in the sandbox menu there is a thing called the "controllervibrotest" or controller vibration test. So let us play the waiting game