I just recently turned UAC off, and what a joy it is to open CCleaner, Smart Defrag, Malwarebytes and WinPatrol Plus with one click of my task-bar. I do not use IE9, so I could care less about protected mode. I do not download music, videos or any file sharing stuff, and I only install trusted programs from either File Hippo or CNET. I don't open any email attachments in my Yahoo! account, no matter how funny they may sound.
I use avast! Internet Security, and WinPatrol Plus. I only use Chrome that is sandboxed in AIS and I keep my OS and all my programs up to date.
To me, UAC is counter productive in that it becomes a "click no matter what" warning. Once I install CCleaner, I shouldn't have to click a naggy warning pop-up every single time I want to run it for the rest of my life.