The N64 standardized the analog stick less than 20 years ago, and the Dual Shock made it practical. Apple's been pretty far out ahead on making multitouch gestures that are a lot more complex than click and drag (even if those efforts aren't primarily directed at games), and the Kinect's got real potential even if we haven't seen much of it realized yet.
On-topic: the first thought I had was that those touchpads simply aren't going to have the precision of a stick. After reading up on their research for haptic feedback, I'm really curious to see what they come up with. I'm still inclined to think they'll be a poor match for fighting games and 2D platformers, but I can see them working with damn near any other genre, retro games and all -- I don't see any reason, for example, why it wouldn't work well with Mario Kart or SM64.
Ooh, and that's another thing to keep in mind about SteamOS -- it's Linux, so there's bound to be a way to get emulators to run on it. And might finally be the goose developers need to start slapping some decent GUI's on top of them. (Linux probably has just about as much variety in emulators as Windows does, but a lot of them don't have frontends and are instead operated by command line flags, rc files, and keypresses that you're not going to know without poring over a readme. And can you fucking believe snes9x isn't even in the Ubuntu repos?)
And of course the nice thing about the hardware being open and hackable is that there'll be plenty of variations that include sticks and D-pads, so there's no reason to worry about that.