DOC,
I may have mentioned this once or twice. I'm divisional IT. Corporate IT is responsible for the FireWall and they use McAfee. They update their pattern once a week.
Being a belt & suspenders (& ductape) kinda guy, I also have InnoculateIT on my Notes server and NAV on my desktop. InnoculateIT catches a whole bunch that McAfee misses. There have been many times where NAV, (partly because of the daily updates) have caught viruses that the others have missed.
I've heard of bad patterns causing grief, but personally haven't encountered any from Symantec (well, a couple back on LANDesk VP abended my NetWare server). I've had my Notes server go south several times from bad patterns but NAV has been rock solid since 7.5 with every (4 times daily) update.
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Give a man a fish and he will be back for more. Slap him with a fish and he will go away forever.