Couldn't tell you. Not only did it take me entirely too long to find the Steam client download from the Steam website, but I haven't been able to get Portal to install. This could be because Valve's servers are getting slammed with tens of thousands of requests (if not more) by people all trying to download the same five gigabyte file. This is not at all surprising, not is it completely unexpected. Valve launches are frequently a little wonky, but give it a week and all will be well.
That said, there are 64 launch titles for the Mac version of Steam, so I went about downloading the other eight that I happen to already own--almost all of them indie or casual titles. And so far everything is performing amicably. There are a couple points of frustration--the first being titles that are available for Mac but that haven't been made available on Steam yet, notably Pop Cap's Plants vs. Zombies (which is odd, since it's one of their more popular titles, and since Chuzzle and Peggle are available). Steam plans to make available another batch of games every Wednesday, so I expect we'll see that one soon enough.
The second point of frustration involves a game that is available for Mac and that I own the license to, but is not available for me to install--Civilization IV. This is most likely a bug, which means it should be fixed before Wednesday. In the meantime, one of the attempts to download Portal will be successful, at which point I'll take an hour to re-battle GLaDOS and be ready to report my findings. And until then, Peggle looks great and plays pretty well.
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