After use it more than 24 hours, here is my current finding.
It very light by Norton standard. Almost unnoticeable when it idling.
It really slow down your CPU (not RAM), when you do anything related to intensive hard disk utilization like defrag and installation. Imagine, I use PowerDefrag GUI with Ms defrag API, one of my CPU core constantly 100%. When I install office 2007 from hdd2 to hdd1, both of my core running at 100%. I need double amount of time to install office 2007 win nav2008 in my system.
You judge it.