IMO, NOD32 is worth paying for. Ki will back me up on this. It's a fantastic antivirus and with threatsense, it picks up on virus traits without the need for a signature to be on file (as stated in the interview). So it's great for detecting early stage viruses.

It's not that expensive either, if I'm totally honest. I bought three, two year subscriptions for all the PCs in the house. It's FAR cheaper than Norton IIRC.