Very late in the day, I know, but just thought I'd mention Comodo Antivirus for Mac: [i was gonna put a URL here, but as I only just subscribed here, it won't let me! But I guess you know Google.... ;-) ]
Short story: there's matousec.com, who do what looks like very thorough testing of Windows antivirus products. Their test results show that Comodo's anti-virus scores 100% on 32-bit windows and 94% on 64-bit (yes, apparently this does make a difference!) But then I noticed that Comodo also have a (free) antivirus offering for Macs. So, I went in search of a comparative Mac antivirus review that included mention of the Comodo product, because I ain't about to assume that their Mac offering is actually any good just because their Windows stuff is!
Up to now, I've been using iAntiVirus on my Macs - and only just this evening did I learn that it's actually a product of Symantec (who, I assume, have bought PC Tools)! So now, a free product from Symantec? Good heavens, what next? ;-)
Anyway, I'd be interested to hear your thoughts - and also to find out what sort of results came out of your testing (if it's all done yet?)