I was not aware that this was such a widespread problem. My experience was not a fluke after all. Good outcome for the both of us.

Last week my experience with PS CC also had it dogging down quite slowly. I scanned for viruses/malware, defragged, and Combofixed it a couple times. This was impacting the machine beyond PS. I thought the problem was not being updated so that is what I did. Immediately afterward, Adobe did NOT remember my previous subscription and I was now a Trial User. After some frustrating online chat with three individuals at their off-shore support facility about why my account had no record of any registered products, I terminated the chat and signed up again for The Photography Plan. Doing that cured my issues. I am now working with PS CC 2017 and blazing through the NEF files from my D800 like never before.
In full disclosure, my system is a Dell Precision tower running Win 7 Pro, dual Xeon processors, 36 megs of ram, 3 dedicated SSD's and a fast video card supporting 2 monitors.

I also own a 290 that came standard with the 3-axis head. Very solid. I recently acquired the Manfrotto XPro Ballhead and it fits fine.