Glad you like it! I am not grounded, actually. If you look at the buttons at about 00:04 in the video, you can kind of see my set up. I have one lead from each of the buttons (any one will work since they aren't polarized), and twisted them all together, then alligator that to a single ground slot to save alligator clips. The remaining leads of the buttons each get their own keyboard input. I used A,S,D, and F. You can then use that keyboard input for machine control, or you can get more complex with it and program in button combinations and midi output.
Right now in Ableton, I've configured these four buttons to launch clips when pressed individually. The cool part is that when I press a combination of buttons, say all four, it will send a 5th midi note to Ableton that triggers effects instead of launching clips.
Oh, for the "programming," I use ControllerMate MIDI.
Hope this helps. Feel free to ask more questions if you want. Also, I would love to see what you come up with!