well i should say that, despite the issues, nod32 is on my system right now
it freaks out with some files - there are a few files that seem to really cause it to scan very slowly.. some dll's that have copy protection and some small .html files. and combined with a flaw in it's ability to cache crc values for files, the weel-renowned speed of nod32 can literally slow down to molasses at certain times.
it took me many days of frustration to figure out that this was the reason that my right click in explorer was taking 10 times longer to pop up than normal, and why my dictionary program suddenly went from opening instantly to taking 20 seconds to open. truly bizarre behavior, and the only solution is to manually exclude these files/folders from scanning. a bug in the exclude dialog makes this even more annoying.
nod32 also has a heuristic engine on by default which can false alarm on some files, and when it alerts on them it doesnt tell the user "hey i'm just guessing about this", which has resulted in some confusion wrt some very harmless programs being accused of having viruses.
with all that said you might think i don't like nod32, but in fact it's really mostly a very nice antivirus with a very efficient feel to it in most respects. i used antivir for a long time and i sometimes go back and forth between antivir and nod32. i just couldn't get used to the interface of avg and some other antiviruses i've tried. i also liked f-prot. mcafee seemed quite nice to me too but i had the feeling it might be using a lot of system resources..