CrossOver Games is a simple installation, even if its underpinnings is crazygonuts. Essentially, games (and applications for the CrossOver application) operate as though they exist within specialized environments contained within the Mac itself. CodeWeavers calls these environments "bottles". For example, the Guild Wars application lives inside the Guild Wars bottle. You can have multiple bottles for each game you want to run, and can configure each of them separately.
If you look at the configurable settings for bottles, it's apparent that what's going on here is pretty much an actual, discrete build of Windows that fires up every time you want to play that particular Windows-only game. There are separate controls for managing tasks in the Windows instance, and you can simulate a reboot for that instance. There's even the option for opening the C: drive and displaying its contents in the Finder, should you need to delve down into that level of software support. For people like me, that's unnecessary, as my Windows Fu doesn't extend to actually modifying registers or editing .ini files, but it's good to know that that stuff is there.
CrossOver Games creates a distinction between Supported and Unsupported games. Supported games include EVE Online, Guild Wars, Half-Life, Shin Megami Tensei: Imagine, Spore, and the Valve Software Steam interface. What this means is that CrossOver Games is ready to let you play these games (with the proper install CD or file) without any monkeying around. If you select one of these choices, you're given a small message recommending a particular flavor of Windows to use, or you can just go with what it suggests. From there, the process is painless. For Steam, as an example, you're given the option to install the client from the Orange Box CD, or download it directly from the Steam website. CrossOver creates the necessary environment, and suddenly you're looking at the ugly Windows interface.
Then it's just a matter of choosing which game you want to play. Opening a game opens CrossOver Games, and it all just functions seamlessly with the Mac environment. Venturing into the realm of Unsupported games, however, is a different beast. From the app: "CrossOver should be able to run many games that use Direct X 9 or any previous version of Direct X. However, there are sometimes problems with particular games." This is where being knowledgeable about Windows guts would probably come in handy.
When setting up the environment for an Unsupported game, you're given the choice of choosing one of four Windows versions for your bottle: Vista, XP, 2000, and 98. And no lie: when I saw that Windows 98 was available, my heart leapt with joy, because it meant that I could stop feeling silly for holding onto my The Neverhood CD for all these years.
Without allowing myself to hope too strongly, I slid the CD into my drive, created the Win98 bottle, pointed it to the CD, and crossed my fingers. Less than a minute later, the screen went black and the old familiar opening Neverhood indicia displayed, meaning I was in like Flynn.
There were a couple of issues: you can't play The Neverhood in a window, for instance. And all the video runs at roughly half-speed with a lot of skipped frames. But for the simple joy of being able, after over a decade, to play one of my very favorite games of all time, I could get used to a ton of even worse issues.
Of course, having successfully installed and played The Neverhood, I was unprepared for when I was unable to install Age of Empires 3, which runs on Windows XP. At some point in the install, I received the message "Error loading the PID Generator DLL. The DLL could not be found!" My tactic of staring at the screen until the message turned into "Oh, nevermind, I found it" completely failed, and that was my experience with installing AoE 3.
Note: If any of my readers understands what this is about, please drop me a line or leave a revealing comment. I fault nothing but my lack of Windows knowledge for this. CrossOver Games is still awesome.
How awesome? Awesome enough that not only can I play The Neverhood, but I can also play Guild Wars without having to restart into Boot Camp, which saves a ton of time. Because CrossOver Games runs Guild Wars, I'm going to assume it'll handle all the subsequent expansions as well; I'll find out sooner or later.
That brings me to something I've been wondering about, and hoping to see for a while now. If CodeWeavers can make Windows-only games run nearly natively on the Mac, is it too much to ask that Apple itself figures out a way to do the same without needing Boot Camp? Isn't this really kind of a proof of concept? What would Apple lose by this? All they'd need to do would be to add this as yet another bullet point in their Switchers campaign: You can run your actual Windows apps directly on the Mac! Steve, I know you're not doing Keynotes anymore, but this would make the ultimate One More Thing.