This is an old post, but I will post it here so others and myself could check this Kerberos authentication setting.
According to MSDN, you could check Kerberos login from application server (or whatever server that the client requested) event viewer (Security). < Sorry I couldn't find the link I read that, it was a long time ago.
If client successfully authenticate using Kerberos it will show
Logon Process: Kerberos
Authentication Package: Kerberos
In KList command it will also display Kerberos, like this picture.
