They've shown a number of SteamBoxes at CES, this article is worth a read.
What do you guys think about Steam Machines? I don't think they're going to make a really big impact; they're are simply too many of them, and it will confuse newcomers/console gamers looking to get a gaming PC.
Many of them also cost well over $1,000 or $2,000, making them just seem like typical pre-built PCs except with a custom OS which would actually be a turnoff for many. I like the ones in the $500 range, I believe they need to make more of those and less of the others if they really want to make a splash.