Steam for Mac, while a welcome panacea against the 17 or 20 Windows users who were clinging to the last hope of their platform (“Macs don’t have any games!”), is not yet a first-class Mac OS X citizen. As a cross-platform system, it is completely expected, and normal, that there are going to be conventions that apply and “fit” in one platform but do not in another. We can’t forget that Steam is a primarily a PC games platform that is inching it’s way toward being the games platform.
Steam is, in a strange way, a great example of Apple’s own thinking (and primary justification) regarding allowing third-party SDK use on the iPhone and iPad platforms. Namely: They’ve created this software that doesn’t feel, in this case, “Mac-like”, or in the broader sense “Apple-like”. Apple has no say in the look-and-feel of Steam. They can’t chastise Valve for Steam’s refusal to work with Spaces (go ahead, try control+clicking Steam and dragging it into another space). It’s a small example, but it grates on someone who uses Macs all day long and expects this stuff to just work.
As a Mac user and a gamer, having Steam on the Mac is great. I’ve spent about $100 on it already. As someone who cares about how things work, Steam is a very PC-feeling application. My gut says many of the explicitly non-Mac design conventions in the Steam application aren’t going anywhere: the strange, dark, non-round-rect windows. Their inexplicable use of ~/Documents to store games and game data. The “Updating Steam” progress window that uses Geneva instead of Lucida Grande (yeah, I noticed). The tiny, non-standard, UI controls.
As for the rest, I hope Valve makes enough money off of Mac users to justify improving the client into something that more resembles the beautiful, usable, interfaces we’ve become accustomed to. At any rate, it’s good to have Valve on board.