This is something that I've never really been able to answer as well as I like: What is the real advantage of using Kerberos authentication in IIS instead of NTLM?
I've seen a lot of people really struggle to get it set up (myself included) and I haven't been able to come up with a good reason for using it. There must be some pretty significant advantages though, otherwise it wouldn't be worth all the trouble to set it up, right?