I agree with a lot of what he says there. I hadn't considered the part about hardware specs. As usual though the most interesting considerations remain around the OS. He might not consider a Steam Box to be a PC, but the hardware is 100% compatible. You could install windows on one if you wanted and put it on your desk. It's the intention to put it under the TV which defines it as a console if anything, which drives the use of a controller and makes non-gaming software impractical. I realise I'm quibbling over semantics, but the distinction is there. I'm with him on the general tone of his comments though, I just can't really see a big market. Still, there wasn't a big market for Steam when it was released either.
Well, if you can install Windows on your Steam Box to make it more like a PC, then what's even the point in getting one? I'd rather get a PC already, with a smaller cabinet.