It appears, via a very interesting viral marketing campaign, that Valve will be releasing Steam, Half-Life, and Left 4 Dead on the Mac sometime in the immediate future. I’ve finished Half-Life 2 on the Xbox (one word: FANTASTIC), and they’ve only released the follow-up episodes on the 360. So I will be seriously considering a subscription.

Update: Confirmed.

“We are treating the Mac as a tier-1 platform so all of our future games will release simultaneously on Windows, Mac and the Xbox 360,” Cook said.