The beta's installer copies the Mac's system drive's contents into a folder on the drive. Open up that folder, double-click on an OS 9 app, and the system kicks off the OS 9 emulation environment in a window. In that window, you can see the traditonal Mac boot process taking place, complete with a zillion extensions and control panels loading up. That takes a while, but the emulation enviroment can be made to start automatically at boot time. Performance isn't too much worse than usual (heh) when running OS 9 apps in emulation. The apps don't share the Aqua look with the rest of the OS, and the menu bar across the top of the screen looks like OS 9 when one of these apps is running in the foreground. All in all, a workable solution, but the interface integration isn't as slick as, say, running 16-bit apps in Windows NT.
We opened up telnet access, and I got in and poked around on the CLI. It's basically Unix, though not nearly as rich an environment as a good Linux distro. It does include God's Favorite Text Editorpicowhich Mac users can use to edit their .conf files. Man, this is gonna be one heckuva transition for some of these ease-of-use freaks. All the Unix basics are therecommands like ls and top, files in the right places, etc. I went ahead and did an "su", then rebooted the box remotely, just for fun. This is a bold new frontier for Mac hacking. And since it's Unix, all of a sudden, I know more about the Mac OS than the most dedicated old-skool Mac gurus. Cool.
From the little I've seen of it, OS X looks like a decent new alternative OS. I hope they port it to x86.