do what *nix does and make the user move their hand away from the mouse and enter a password for a privileged user in order to proceed.
You can do that as well - set up an admin account with a password but don't use it. Log in on a limited privileges account and whenever UAC requires admin rights you need to enter the admin password... much like *nix.
The only real problem is, again, legacy apps that'll make you enter the admin password every time you boot them up (it's not much of a faff if you're only having to enter the password when there's a software install/upgrade).
You only get the UAC prompt with an "OK" click-box if you're already logged in as an admin; it's a bit like running as a pseudo-admin really since you'll still need to grant access to programs via the UAC prompt on a per-instance basis.
Unlike previous incarnations of Windows - it seems that with Win7 (much like *nix and OSX) the user really is the weakest link - and boy are there some weak links using Windows ;)