Yeah, I wouldn't bother with Norton/Symantec since their support for OS X is nil for some time now.
At our school district, they are using Sophos Antivirus on the PCs and they also have a Macintosh client. I don't know if it's Leopard ready though. So far, they've been OK on the PCs but I haven't tested on the Macs yet. I haven't found a virus that would infect a restricted user's account beyond the actual home folder and account, especially since most of the malware out there has only required administrative authentication to actually execute (something that a restricted account wouldn't have access to).
http://www.sophos.com/products/enter...mac/index.html
From the looks of the site, their current product is Leopard ready.