The grid is indeed connected to the surface pro which is running a clip chopper patch in M4L. All devices are connected through the powered USB hub seen in the top right as this is a Surface Pro 3 with only a single USB port.
I have been using Ableton on the surface pro exclusively for live performances and for that, it has been great. I really dislike the feeling of using midi controllers to launch clips. This setup has allowed me to avoid controllers (with the exception of knobs, I love knobs) and get closer to the tactile computer instrument I've always imagined. As far as composing on the Surface pro 3, here is video that covers the subject in great detail