Seems like the SteamBox has the same issues as SurfaceRT:
It's an unknown quantity.
Has little app support compared to competitors.
Existing apps must be ported to it and some rewritten altogether.
There are already many other options in the marketplace that provide a similar function.
That's largely true, but the comparison is a bit of a stretch.
A tablet (or a smartphone, or a laptop) can be made indefinitely useful with just a handful of applications. By contrast, a game console needs a constant stream of titles being ported to it or it will soon become as useful as a doorstop.
Also, if you want to - say - browse the web, it doesn't matter much which browser your tablet provides, as long as it does a decent job. But if you want to play some specific game, no substitute will ever do.
Bottom line: the Surface doesn't have it easy, but that's a walk in the park as compared to a new game console.