I have a gaming desktop that I built, and I think that if done right, Steam machines can succeed big time. If I had the disposable income, I'd buy one of the forthcoming boxes in addition to my PC but it would have to have several demanding key features which I'm not sure will be present, at least in early iterations, and which may require windows: a large variety of titles from the Steam store including older games and the ability to play Early Access titles (I play lots of Early Access games; a big part of my PC gaming experience); the ability to connect to my PC to offload games and free up storage space, then quickly upload them (Valve should offer their own version of a SteamMover type tool), or add game saves, skins, and custom config files; option for background downloading during play and low-power idle mode where the system can be left on and download game updates as they are published; this one is big - the ability to play at least the most popular mods for major games like HL-2 (Valve should create a new SDK that fixes issues with many of the older mods that were broken with Steam Pipe); Uplay and Origin integration; keyboard and mouse support to play FPSs like Counter-Strike and RTSs just as precisely as can be played on desktop; good headset support for online, preferably with teamspeak integration; a nice web browser to quickly bring up review sites, walkthroughs, etc. - ideally Chrome including certain extensions/apps like ad-blocker, evernote, etc.; good integration of the Steam forums and other community features; apps for streaming media like Hulu, Netflix, Youtube, and ideally the ability to stream music playlists from computer as on xbox; lightweight, nice form factor, with 4 controller support; an API so software developers could build apps and modify certain existing desktop software - let's say mumblecore - to work on Steam machines; and finally, a big one, excellent video-capture and twitch.tv streaming support with the ability to plug in an external HDD or SSD for storage. All these things I'd pay $500-$800 for, negotiable - third parties would swarm to the machine and nobody would have a proper excuse to play consoles again.