I downloaded and installed El Capitán this morning. The download was calculated to take 45 minutes but I think it was less than that. The installation took about 30 minutes. Everything went smoothly. I had to reset a few preferences (notably a custom keyboard shortcut for Dashboard) and reinstall Java 6 for Photoshop CS5, plus I had to update two utilities (Cocktail and OnyX), but everything seems to be as I had it in Yosemite.
I'm keeping fingers crossed that nothing major will rear its ugly head. So far, so good.
Jon
macOS 11.7.10, iMac Retina 5K 27-inch, late 2014, 3.5 GHz Intel Core i5, 1 TB fusion drive, 16 GB RAM, Epson SureColor P600, Photoshop CC, Lightroom CC, MS Office 365
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