Steve,
I have recommended (and run on several networks) AVG Anti-Virus Network Edition. It too has proven very reliable for me, has a reasonably small resource usage on the stations and allows for central management. I've got it running on several Server boxes, and have not had any of the issues which have been reported with SEP.
http://www.avg.com/us.product-avg-anti-virus-network-edition for more info.
-Matt