The Steam for Mac client has been in the hands of gamers for a week now and Valve is collecting some useful data about Mac users. Among the statistics the company has gathered so far: two-thirds of Steam for Mac users run on laptops, and after one week, 11 percent of all Steam purchases are for Mac. One surprising result, however, is that the same version of Portal is five times more stable on Mac OS X than on Windows.

Mac OS X has never been the preferred platform for gamers, despite its support for the OpenGL 3D graphics framework. Part of the issue is that graphics hardware drivers for Mac OS X just aren't as well optimized as they are on Windows. In an OpenGL benchmark comparison between Mac OS X 10.6.3 and Windows 7 x64 by Phoronix running on identical Apple hardware—in this case, a 9400M-equipped Mac mini—Windows 7 trounced Mac OS X in terms of raw speed.

Performance-wise, Valve believes there is plenty of room for improvement when it comes to better leveraging the underlying Mac hardware. "We'll catch up," said Valve developer Jason Mitchell on a recent episode of The Conversation. "Apple is certainly motivated to work with us—we're working with them; we're working directly with the hardware vendors. We know it's the same hardware, but you boot up a different OS, there's different performance characteristics."

Valve founder Gabe Newell said the Mac platform and its support for OpenGL represents a great opportunity for the company. "We're definitely not as mature on the Mac as we are with our work on the PC," he said.

"We've been shipping games for years on Windows; we've been shipping them for a week on the Mac," said Mitchell.

Beyond raw performance, however, Mitchell noted that the Mac has other advantages. For instance, with just a model and OS version, programmers can more easily recreate bugs and profile hardware performance on the Mac. Windows users benefit from faster driver updates while Mac users might have to wait for Apple to roll out a point release, but the proliferation of possible hardware-software configurations makes it much more difficult to pin down problems.

Also, said Newell, "what's sort of surprising is how much more stable our games are on the Mac." Looking at the early data available from the Steam client, "the Mac is five times more stable than Windows" when using the metric of minutes played versus number of crashes.

Newell remarked during the podcast that graphics performance is much less of a concern overall compared to finding ways to offer a better user experience, such as the greater stability on the Mac. "I think we're starting to enter a period where graphics performance is sort of a solved problem," Newell said. "We're moving away from loss-leading graphics approaches [of consoles] toward more of a service platform. It's less about pixels per second and more about micro-transactions and identity."