Valve had originally intended to include cross-platform support for PC, Mac and PS3 versions of
Explaining the decision not to include it in Global Offensive after all, Valve’s Chet Faliszek said “The beta has proved we want to update not just the beta, but the game itself post-launch frequently on the PC. To do that we need to separate the platforms so one doesn’t hamstring the other.”
Reading between the lines, that suggests it wouldn’t have been possible to offer regular, concurrent updates on all platforms to keep each game version the same.
The game is currently in beta, and you can sign up for that by filling out this here survey.