You already know that Half-Life 2 for Xbox, Xbox 360, PlayStation 3, PC and OS X is excellent, but have you tried it on Linux? Well, yes, technically speaking, you couldn't actually play that version until this week when it launched on Steam for Linux, but our question stands! Yeah, that's what we thought. Now that that's straightened out, we might warn you about the beta nature of HL2's Linux launch. Like other Valve titles recently released to Steam for Linux, Half-Life 2 is merely a beta for now. Should you already own a copy for another platform, it'll show up in your Steam library as available for download like any other crossplatform game. Of course, you're probably too tied up with Half-Life 2's recently added Oculus Rift support on PC to think about a plain old keyboard/mouse experience. And hey, we can't blame you for that.
Interestingly, Valve's internal Steambox is powered by Steam's Linux version; it wouldn't be hard to imagine Valve scaling up its Linux game library ahead of the retail debut of various Steamboxes (or Steamboxen, if you will). That remains to be seen, of course, as Valve's made no official announcement regarding that project's availability.