+1 for NOD32 (its excellent). The only drawback is it is updated only when you are connected to the net. AFAIK you cannot update it if you dont have an internet connection i.e. no concept of DAT files, etc.
I've been using NOD32 by 2 years now... and never had a problem with it. Indeed a best one followed by KasperSKy n Bitdefender
No Viruses yet, no roootkits neither Spywares. And to tell you all, I use NOD32 + Default Windows XP SP2 ( now SP3 ) Firewall. (add to it daily downloads from Torrents, Limewire etc.)
But the only concerning problem I found was Windows Security alert. BUt now with SP3 installed, That has gone