What would you stream on it?
I actually have a bunch of controller appropriate games on my Steam account that I could see working with this. Deus Ex, Batman Arkham Asylum/City, just about all the GTA games, Beyond Good and Evil, The Walking Dead, Fable, Skyrim, Bastion, Space Marine, Super Meat Boy, Assassin's Creed II, Psychonaughts, Saints Row 2, Ghostbusters TVG, Dreamfall and the three Crystal Dynamics Tomb Raider games. I could probably manage with some of my FPS titles like HL2, Portal/L4D 1&2, as well as the earlier Telltale games, but it wouldn't be ideal. Not sure about the Bioware RPGs since everything post Jade Empire appears to have been ported to one console or another, so I assume it's just a matter of fiddling with settings to get the controller options turned on.
You're right though, it won't be suited for the likes of RTS games or MMOs, but then you're not likely to be playing them on the move anyway, so since those make up a relatively small percentage of PC games as a whole, it's a bit of a minor issue as far as I can see.