I'm working for the day at the annual UK Oracle User Group event in Birmingham - there are two thousand delegates. We have a large stand upon which I'm demonstrating Windows Vista.
I've been showing IE7 as pretty much everyone else does.
I've also shown Least User Access (LUA) whereby users can request privilege for specific tasks rather than running with privileges the entire time. As an example I have a user named Toby who's a regular (non-priv) user as you can see below. Incidentally the command line is so much richer @ Windows Vista - it's much easier to cut to the chase when finding out what's going on.
Whilst logged in as Toby I attempt to change the system time as you can see below:
Notice the "Unlock" button. Upon clicking it the person using the machine is prompted to enter the credentials of an account that has the required privilege as you can see below: