Thanks guys for the answers. I appreciate the information. I think I probably don’t need antivirus right now, but I understand that some people use it out of an abundance of caution. I’m glad I don’t absolutely have to use it yet, one less thing to worry about on my Macs. On PCs, the antivirus issue has become less of a problem, with stronger CPUs and free programs like Microsoft Security Essentials. The slowdowns and expense of antivirus protection are far less than they were. But it is still more of a pain than on Macs.
I’m not as concerned for myself as much as avoiding the possibility of emailing some infected file to a friend with a PC :)