Golden Triangle with Snow Leopard for iCal Server

I'm planning on upgrading my Tiger Xserve to Snow Leopard soon. The server is primarily a file server (AFP & SMB ), but I hope to be able to use it as an iCal server as well. I've googled for any possible issues with this setup, and it seems that "Augmented Users" are having trouble. What is an augmented user? Has anyone else done this?