Okay, why should I buy a gaming PC that can't be upgraded and requires to run Linux on it? I mean if you look at gaming PCs, there is a huge variety to choose from. Samsung, Dell, Sony, Toshiba, IBM etc.

Valve probably is working hard to have publishers optimize their comming pc games to the configuration in the sbox. So that way it should be able to keep up with high end configurations for a bit, although the sbox itself most likely will be ~high mid tier hardware.

If that ends up being a success I expect Valve to have fairly short cycles, like releasing a new box all ~3 years.

It could be convenient. Sure I can bring my tower over to the tv but it simply doesn't fit in my av stand and always has to go back to the desk after anyway.
Depending on price why not get a second box. I see it the same as buying my old games on gog.com. Sure I can dig up the box and search around on the internet to get them to run on win 7, or simply buy them from gog and avoid the hassle.

It won't be an option for gamers that want the latest sli gpu upgrades and mod games to their breaking point. Yet those are a minority. If it allows you to play games from steam sales with better performance then next gen consoles, plus a huge library of old games and indie games, it will be a success.

It won't be a huge success but I don't think it'll be a major flop either.

They are all seriously overpriced and some of them still aren't that good.

If there was a box people could trust to play all the games they want to play, no research required and for reasonable cost, isn't that what people want out of a gaming PC?

Upgrading a PC is something that a tiny fraction of the market care about or would want to do. Anyone who's into that isn't part of Valve's intended market.

I dont think it will be huge, but I think it will be a success. I think it will make money for steam, and provide an alternative to home consoles (and cheaper games as long as they dont institute a fee like ms/nintendo/sony). But I think consoles are on the way out so I am not sure of the long term success of it.

Yeah, but every PC and every console offer exactly that. And most of the PC games on steam are designed for... wait for it... the PC! So some sort of controller would be required, which would automatically kill a big part of the PC gaming fanbase they have experienced with for the past years. And going after the console gaming fanbase means going head to head with MS, Sony and Nintendo and I don't see Valve having the resources for this.

I think it will be a challenge definitely. Valve have a cult following and that will help if they make their own games exclusive.

One part that could side with them are the purists who can't accept new control methods. I think it can have a bit of success if they sell at profit.

Oh boy, you are declaring dead a "console" that hasn't even been announced, there's no confirmed info at all.

I don't know what Valve wants to do with the Steam Box. It almost certainly won't compete with the big 3. It doesn't have broad appeal, and it likely won't be powerful enough for PC gamers. It's going to be a niche product, but I can't figure out what the niche is. I guess we'll have to wait and see the pricing/specs.