My clients have used it before and its been an utter POS - like steve said, there are times when norton becomes a virus itself, with backdoors and buffer exploits that get taken advantage of by those who write malware. Conversely, just because its not a resource hog, doesnt mean that it actually has a thorough scanning engine - McAfee used to have that problem on their consumer level software up until 3-4 years ago, however now McAfee and Trend Micro (as well as CA -Etrust which ironically is also owned by Symantec) are currently the major corporate AV's in use, generally because people do not trust Norton branded AV's based upon their shoddy consumer level software.
I will however point out that my criticism for norton is solely based around their consumer rather than corporate software, however actually having seen the corporate edition I can't actually say that I'd trust it further than I could throw the box it comes in.
-D