A somewhat long, but very interesting, article on experimental evidence of the benefits of using LUA (least privileged user accounts). An important point they found...Power User isn't the answer. The findings indicated that removing a user account from the Administrators group can dramatically reduce the impact of current drive-by malware installs from the web. The use of normal user accounts on a fully patched machine almost completely prevented the tested malware from installing. By contrast, both the Administrator and Power User tests allowed a substantial amount of adware/malware to infect the machine.

Food for thought.