Hello,
I published a tutorial of how to implement a SIP SIMPLE Presence & XCAP server with latest Kamailio/SER version. You can find it at: http://bit.ly/btrJij
Last build of SIP Communicator softphone was used to exemplify some use cases.
xcap_server is a new module in upcoming v3.1.0, I have tested it with several SIP clients, but I have to say is not easy to find one that implements many presence & xcap extensions (filled already couple of bugs so far). So consider it a young component by now, however, with it inside our SIP server, deploying a SIP presence server becomes trivial.
Hope is helpful, Daniel