I see that controller as falling into the same category as a touch screen, not necessarily like a thumbstick.
And that is exactly where I think it's going to barf.
If you look at the "Smart" phone market, you'll see the problem. You have, for the first time in an absurdly long time. a entirely different HID with 100% product penetration. So developers given free reign with such an interface do what? Try to emulate a joypad and button or keypad or whatever. Some get the idea (Angry Birds) most are still ---smurfing--- clueless (SEGA).
Valve's Owl has no chance of having that kind of penetration. Their only hope is if the developers "catch on" to the possibilities and write software that take full advantage of it, not just emulate an existing control scheme Otherwise such a controller is just going to end up as another forgotten piece of ---smurfy--- hardware.
According to some, was it mentioned here? Vslve is claiming this Owl will be fully hackable. I can't really tell if it's because Valve is clued into the hacker culture or hedging their bets and hoping enough non-Steam people will pick this up to make the venture worthwhile.