I feel quite safe using NIS 2012 as my only real time protection as I have since NIS 2010. I enjoy all the new features and improvements NIS brings to the table. I must say however 2012 does have some bugs that must be fixed and all one has to do is visit the Norton Community Forum and read about others experiences with this product. I myself have only experienced a few minor bugs however. I feel confident Symantec will have these issues resolved in short order.
http://community.norton.com/t5/Norton-Internet-Security-Norton/bd-p/nis_feedback