Hey Kenneth,

Thanks for your reply. I apologize if my original post seemed harsh, I've fought some extremely frustrating battles with kerberos in the past and want others to avoid my pain and anguish.

As for automatic spn registration, there is a recommendation against using automatic registration on a cluster:

http://blogs.msdn.com/b/psssql/archive/2010/03/09/what-spn-do-i-use-and-how-does-it-get-there.aspx (which I just found about 15 minutes ago, the rationale is in the comments)

My original thoughts on manual being better are due to consistency with other Microsoft products that don't auto-register themselves (SSRS, SSAS, Sharepoint 2010 components, etc), and explicit registration forcing DBA's and Sys Admins to become more familiar with kerberos configuration. Unfortunately, the easy way to get spn's registered is to run sql as a domain admin account. The second easiest is to ask a system administrator to run "setspn.exe ...". The third is to grant the specific permissions to the service account (as you mentioned).

As for constrained vs unconstrained,the current guidance from MS for Sharepoint configuration strongly pushes constrained delegation. Because constrained -> unconstrained doesn't work (and is very hard to trace as the culprit), I would only recommend configuring constrained delegation on your sql service accounts. I believe that the guidance from MS recommending unconstrained delegation for SqlServer hasn't been revisited in several years (could be wrong though)

If you wrote a follow-up article on configuring kerberos for SSRS and/or SSAS, that might be helpful as well.

I hate seeing people avoid kerberos because it's too hard to get configured or they don't know how to troubleshoot it.

thanks!