I try to run as a limited user for the obvious reasons. But as a dev it can cause a bit of havoc every now and then. That was until someone in the office put me onto Superior SU.

This is the niftiest tool. It basically uses the hidden multiple desktop implementation in Windows and creates an "Admin" desktop. (Well, you create it, but it's managed by Superior SU). Then, whenever you need admin access, you right click on the tray icon and choose your admin desktop. It'll ask you for a password (you can stop it from doing that, but that kind of defeats the purpose of securing your machine...)

Anyway, download it and try it out.