I downloaded and installed the OS 10.11.5 update from App Store. It weighs in at 907 MB and installed very quickly. The dialog box estimated 20 minutes to complete the installation but the actual time was closer to 5. All seems well.

Also did the update, but used the combo updater. So far all is good. For those that want the combo the website is https://support.apple.com/kb/DL1876?viewlocale=en_US&locale=en_US

My download weighed in at 1.77 GB (update from 10.11.3, not x.4). On a laptop connected by wifi with a blazing 6 (six!) Mbps download speed I saw estimates of 1.5 hours to 2 days. It ran overnight and installed with no problems.

I had no problems with the 628MB automatic-in-the-background d/l or install of the 10.11.5 Delta, but I was surprised to find the Safari 9.1.1 update included.

I hadn't known about the Safari update (and mine now reads at 9.1.1) but I hadn't known that iTunes was included. Of course, I neglected to click "more" when I went to App Store. Had I done that, they would have been revealed. That explains why my update took up more space than yours.

Which one of those"hadn'ts" should be a "had"?

My 10.11.5 didn't included the iTunes update which also d/l'ed automatically in the background and, surprisingly, was either four or five separate packages. I didn't even realize they added up to the update until I looked at my version number after I installed them.

(I'm not sure what you mean by "click more".)

So did I, on both of my Macs. Also, I downloaded, and installed, iTunes 12.4 separately. As with you, all is good.

I wonder if this will be the last El Capitan update to be released, given that the new OS, 10.12, is due out sometime in the early fall (just like El Capitan's release last year, and after the final update for Yosemite, OS 10.10.5).

I wonder if the "full" OS 10.11.5 one from the App Store includes iTunes 12.4? Anyone know?

I just checked my 10.11.5 Delta d/l from the App Store with Pacifist, and the iTunes update isn't included, but as I've already said, I got it as four or five separate packages.

I have seen situations where several updates are only listed as one. Under the one that is shown, there is (or at least has been) the word "more" shown. Clicking on that word reveals all the updates and enables you to install them separately. Otherwise, clicking "install" installs all of them. I assume that App Store still does that.

Next time, I'll remember to click "more".

I don't remember seeing "More" when I visited the App Store, and I was looking, not necessarily specifically for it, but for something along those lines.

I'll have to keep my own eyes open next time.