Steam on OS X isn’t particularly running as smoothly as on the PC. On the same computer, Steam games will generally run 30-50% slower on the Mac than they do under Windows, a fact Valve is familiar with. Now they’ve announced that they’re working with Apple and Nvidia and ATI on performance on the Mac, both in terms of Steam software and drivers. Valve promises that performance will improve, but didn’t provide a time frame.

Mac gamers rejoiced after Valve unveiled that Steam was coming to Mac, however, it now seems that while Steam is on Mac, it has taken a massive performance dump in the transition. According to several tests, including at Tom’s Hardware and AnandTech, Portal on OS X is up 80% slower on than compared on the windows version, and is on most MacBook laptops, even high end Pros, unplayable at anything but the lowest settings. Hopefully Valve will improve performance in updates.

After a successful beta period, Valve has announced that it plans to roll out Steam on the Mac tomorrow. The two launch titles so far only include Portal and Torchlight — both excellent games — and Valve’s other heavy hitters are to be released on the Mac as well, including Team Fortress 2 and Counter-Strike Source.