I have a very small environment, and only I can make AD or GP changes, so this is really watching for outside attacks. I have yet to have it tell me something I didn't know I did the day before.
Last Friday (1/2/2015), while I was on vacation, I get an email listing all of my group policies as modified, under General/Delegation, and no other information, see attached image of email. What is General/Delegation? There is no such category inside each policy.

Also, there were two polices that showed 1 category each as changed. Changes that I had made back in the summer. I looked at the actual policies on the server manager, and sure enough, they all showed modified dates as recent as last month, and as old as July 21st, but nothing in the last 4 days. The real question is, why did I get a report at all, if none of the policies have actually changed in several days or more.
I do have a report for the change I made on 12/30, and it did arrive the next morning, as it was supposed to do.