I have no idea what this will be like. It seems kinda crazy but I did once own a PC joypad with a force feedback analogue d-pad (think analogue stick mechanism but visually a d-pad shape you rotate about) that could give you resistive force to your pushing. PC is home to crazy experimentation (and if you want to play a game with a traditional controller or even mouse/keyboard it sounds like you can still do that - this is just a crazy option they think is really cool and bridges the gap).
Considering Sony finalised the DualShock 4 price in the UK and we get to pay $90 for a controller over here, I sure hope Valve have worked out how to make something like this reasonably cheaply (a screen on the device is Dreamcast cool but not conducive to making for an affordable thing). This looks like the kind of thing they need to get out there so people can try it before anyone knows if their claims are true (my living room TV sits on a desk, because I've got a weird flat, so I don't mind switching between joypad and mouse/kb while I game so maybe this device isn't for me).