It's way too early to tell to be honest. We have few specs and have no idea how game support will pan out beyond Indies and Valve games. I suspect we'll see some AAA titles from third parties but the first year will almost all be Indie games.
I would recommend waiting a year after they're released to see how well supported the Steam OS actually is. If it looks like support is growing and some interesting games are coming out (that aren't on WiiU) then jump in and buy a Steam Box. Otherwise, you may spend a lot of money to play some Indie games that could be played on a very cheap PC.








