As you would expect, NAV offers real-time, scheduled, on-demand, IM email scanning options. Updates are pushed out extremely speedily - once every 5 to 15 minutes, on average.
InSight is a performance feature that's new to the Norton 2009 product line and it's also one that is particularly interesting. Here's how it works. Symantec collect information from their community of users about the files that are present on their computers (but don't worry, no personal information is collected and easy can opt out completely if you wish!). The most common files are analalyzed and, if found to be safe, excluded from scanning which results in faster, fewer and shorter scans. That's a very basic explanation - a more detailed one can be found in the Symantec blog.