First, thanks for picking this up Jason! Just to add on to interr0bangr's post, the minimum would be the A, B, Y buttons on the controller. The A button works just like the center button on the slim remote and is, obviously, the most important button that needs to be supported. The B button does back in a couple games and apps where the arrow key from the slim remote just exits the app. The Y button is a menu key that is unique to the controller, an example wold be the NBC News and streaming app.The X button doesn't seem to have an important function non-game function but I am still pretty new to the Shield and AndroidTV. Then, for me, the right analog stick is important as it controls the mouse movement in non-AndroidTV apps.I would add that the right center button on the controller, the one in the sliver area that looks like a right arrow with a line on the left, seems to work as a dedicated play/pause button which the platform really needs. An example would be the Youtube app where pressing the A button (or slim remote center button) brings up the OSD menu where you have to navigate to the button you want to press and then press it. That dedicated play/pause button is one touch play and pause.