If you have an existing valid subscription to Norton Internet Security or Norton Anti Virus (any version), you can now upgrade to the new 2010 versions for free.
This also applies to the half price deals for NIS 2009 posted elsewhere. Buy 2009 and upgrade to 2010 free!
You need to go to the main Symantec web site, click support, then Norton Update Center and either let the automatic product scanner check your product or click the link for "Choose My Product Manually" to select the upgrade package.
If you've encountered problems in the past with Norton slowing your computer to a crawl, this has been resolved and it's no longer cpu or memory intensive. In addition, the new version debuts a new kind of virus detector that doesn't just rely on virus signatures to detect suspect files.
If you have a current subscription to NIS or NAV then this upgrade is a must!