One other UNIX mechanism introduced in Mac OS X is the presence of real multi-user systems. This means that you can create a user account for someone with limited permissions so you don't have to worry about them jacking up the system or your desktop. Some users might not like it, since they are used to having full control over everything, where as now, you need to be an administrator to install programs.
There is also a root account that is rarely needed, but it's there.

Like Windows XP OS X displays a graphical login screen with a bunch of icons representing the users.

Mac OS X bundles iTunes by default, unlike previous versions which required you to download it.

And of course, Mac OS X includes a revamped version of Internet Exploder which is still just as much of a fail as it was before.

Shutting down Mac OS X 10.1.