On the enterprise side, it's much much worse. AFP is heinous. Their kerberos implementations are painful.
They actually have checkboxes in OS X server config screens that say: "Prevent man in the middle attacks? Yes or No?"
As for kerberos, that is painful on any platform. At the moment at work I am trying to figure out why Mac OS X takes 10 minutes to connect to a Windows Server 2003 based file share, all I see with Wireshark is a bunch of Kerberos stuff being thrown around, whereas Windows clients connect without issues, but without ever attempting to use Kerberos.
anyway, hope you figure out the problem. :)
I don't really understand the point of OSX Server beyond possibly render farms (for music / movies)
Small businesses, because they are very easy to manage.
More importantly though, Mac imaging. You can't run DeployStudio on anything but a Mac running OS X Server. So if you have more than 5-10 Macs to manage, having an OS X server around is a no brainer. It doesn't cost much and it makes managing & imaging Macs as simple or simpler than PCs. This is by far its most legitimate use.