Mac Steam itself seems to work just as well as its PC counterpart does. You can browse both the Mac and PC game libraries, manage your account, start and stop downloads, etc. Everything you can do on the PC you can do here. You can choose to download your PC games from Mac Steam if you prefer, which might save you time from having to switch platforms.

The first thing I did once Steam was fully installed and patched was to browse the Mac library, which boasts 64 available games, many of which bear the Steamplay logo. Steamplay is Valve's concession to the dual-platform player. If you already own a PC copy of a particular game, you can download the Mac version (if there is one) for free. When I saw how many games featured Steamplay, it made me excited to think that there were that many Mac ports of existing PC games.

Yet I discovered that not all of these games have Mac demos. I wanted to test for myself how it would be to download Luxor 3 through Mac Steam and launch it from the interface. During the download wait, I noticed a blurb mentioning that the game was "not available" on the "current platform". This turns out to be true for the vast majority of the 64 games that comprise the Mac Steam library. The trouble is, I know for a fact that a lot of these games are available, and most of them do have demos. I clicked through to at least ten Steamplay games without finding a Mac version demo. On a related note, I can search the library for Mac games, and I can search for Demos, but I can't search for Mac Demos. I don't know why these Steamplay titles show up under the Mac tab if they're unavailable. I can only guess that they're on display as an announcement of intention to make them dual-platform at some future time.
With the exception of Portal and Civilization 4, the Mac game library consists mainly of casual titles, many of which have been available for some time. The Steam Play Indie Pack and Telltale Steam Play Pack are great bundles for value, but Mac players who have been chomping at the bit for more high-end games like the old Macsoft port of Unreal Tournament 2004 must continue to wait.

Portal is currently available for free and sets the bar for all future ports of Valve games, so I was eager to test out its performance. After waiting impatiently for the download to finish, I hit Play in the interface, only to be told that my Mac doesn't have the necessary hardware requirements to play the game. My video card is the culprit; my Nvidia GeForce 7600 GT is simply out of date. This is a good call to action for Mac players who want to play Left 4 Dead, Team Fortress 2, and other Valve games: you'll need to make sure your system uses at least a Geforce 8 or ATI x1600 video card. Generally speaking, if your Mac was produced within the past two years or so, you should be able to meet the requirements.

At this point, my frustration with the service overwhelmed my desire to continue to tinker with it. I only returned to it a few days later to see if things had changed at all, which they haven't. I was able to download a demo of And Yet It Moves, and that experience at least turned out fine. It was a quick drop, easy to launch from Steam, and the game played well.

Long story short, there is still a lot to be hopeful for with Mac Steam, and I don't want to dump on it too hard because it is just starting out. But the fact that Steam doesn't have demos for games that I know do have demos is a little mystifying. There is no reason for me to use Mac Steam right now, and that's a shame.