Always wanted a touchpad in place of the right stick, but touchpad for movement can't be ideal. And I think there should be four or five discrete click zones on the touchpad instead of one in the center to double as d-pads or extra inputs. Three sets of shoulder buttons are a welcome change to keep your fingers on the pads.
Compatibility is the other problem. The nicest thing about xinput/360-pad is that you plug it in, all the hud elements change, and it just works. The Portal 2 example uses keyboard and mouse bindings. So, when the game tells you to jump, it'll say "Press Space to Jump" and that's L3/center click on the left touchpad? or do developers now support kb/m, xinput, and third steam controller option? if games are to use that fancier rumble, it'd have to be a third option, or that rumble is part of the controller (i.e.: it rumbles as your thumb reaches the end of the touchpad, regardless of software).
Also doesn't seem as versatile as a regular 360 gamepad. Guessing it'll be excellent for shooters, but something like Batman or AssCreed or any indie 2D platformer? it's a strange thing.