With Mac OS X, if I need to make a change to a system setting or install software in a location that I don't have read/write access to, I have to authenticate to perform that action. For example, I want to change my IP address for my wireless connection, and my system is set up to require authentication to do such things. With the details expanded, I have a fair bit of information. First, I have to know the password of an administrator user for that machine. If I don't, then even physical access isn't enough; I can't unlock that preference pane. Second, I know the right it wants me to authorize: system.preferences (although I may not know what that means, it's there at least), and I know which application is requesting that right.

If I attempt to perform the equivalent action in Vista, I don't actually have to "authenticate" anything. There's no need for a password. Anyone sitting at this computer can take this action. What you see for UAC as an administrator is basically a dialog that says, "You want to do this?" I don't get any information about what I'm asked to approve -- all I get is a really long GUID-type number that's of no use whatsoever.

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That illustrates the three worst aspects of UAC and why I think it's going to be called "User Annoyance Control." You get what is essentially an "OK/Cancel" dialog that most users will hit "OK" for without thinking, you may or may not get useful information as to what is going on, and you get locked out of your system until you deal with this. I have a problem with seeing how annoying people is enhancing security. When I say "annoyance" I really mean "infuriate," because you get UAC dialogs all over the place, and you're never sure when or why you're going to get them.