Shelly Bird has a great (and bravely honest) column just released on the November online TechNet Magazine on why you should use LUA.
Excerpts to get you to read it (out of context - you should read the whole article):
"There is a special kind of arrogance involved to insist that it is absolutely necessary to run all daily business with an account that has local administrator rights. It’s like riding a motorcycle down the highway, hair flowing in the wind; it feels great, except for the fact you are at the mercy of any flying object. Running as power user is like driving a convertible. Running as a normal user is that safe little car with the airbags—if you hit something, it might crack the windshield, but you’ll keep driving and get to your destination.
"Not only that, but there is something degrading about willingly relinquishing that Admin power, a nagging suspicion that doing so is a sign of weakness, an inability to hold one’s IT liquor. Only hardcore security consultants run as Non-Admin, and we all know they’re kind of paranoid.