The bindings mount on a metal plate. The plate can be oriented in snowboard mode or ski mode. In ski mode, there is only a single pin attachment, allowing for a free heel.
I was going to just get a Voile cause you get the hardware, board and skins all together. They have too models now, with the major difference being stiffness. The Prior sounds pretty good too. Apparently Never Summer (CO company thats made boards for a long time) will also do custom splits now.
FYI SC, the new burtons use Voile hardware. They canned their hardware development and are just doing the boards now.
I havent used em, but the approach skis seem like a silly option. Less float and more weight on the downhill. This is just my perception from what I've heard though.