Today, the Half Life 2 series was made available for cross platform gaming between the PC and Mac. The update included 45 new achievements for the series, Steam Cloud support for save games, and graphical effect improvements.
Half-Life 2 took 6 years to build, and here almost 6 years later we get to release it again - this time on the Mac. As of today Half-Life 2, Half-Life 2: Episode 1, and Half-Life 2: Episode 2 are available on Steam on the Mac. They're SteamPlay titles, so if you own the games on the PC you already get them on the Mac, and if you haven't played HL2, buying it gets you access on both systems. Half-Life 2 has one of the highest critical ratings of any Valve game, with a 96 on Metacritic, and has seen consistently high player numbers on Steam with over 216,000 users playing it in the last month.
Also, if you've never played through the Half Life 2 Series, please do it now. :)