That situation is set to improve now that Valve has adopted the Mac as a "tier one" platform alongside Windows and Xbox 360.
"Our Steam partners, who are delivering over a thousand games to 25 million Steam clients, are very excited about adding support for the Mac," said Jason Holtman, director of business development at Valve.
"Steamworks for the Mac supports all of the Steamworks APIs, and we have added a new feature, called Steam Play, which allows customers who purchase the product for the Mac or Windows to play on the other platform free of charge.
"For example, Steam Play, in combination with the Steam Cloud, allows a gamer playing on their work PC to go home and pick up playing the same game at the same point on their home Mac. We expect most developers and publishers to take advantage of Steam Play," added Holtman.
Games including Counter-Strike, Portal and Team Fortress 2 will be available to run under Mac OS X in April.
Valve's first simultaneous release for Mac and Windows will be Portal 2, expected in time for the Christmas 2010 buying season.
"Updates for the Mac will be available simultaneously with the Windows updates. Furthermore, Mac and Windows players will be part of the same multiplayer universe, sharing servers, lobbies, and so forth," explained Cook.