The latest update broke Lightroom and made it unusuably slow. It is way past "excruciating", this is really unusable. Simple tasks like cropping simply no longer work, every move of the cursor with one of the nodes requires a 30 second update and it is no longer possible to watch cursor and rectangle movement in real time. Nothing changed on my computer, the system is all up to date, the only thing that changed is the latest CC update.
Photoshop appears to be working normally, although it seems to be incapable of stitiching some multi-row panoramas in auto mode.
Revert back to Lightroom 6.5.1/Lightroom CC 2015.5.1
Follow these instructions (where it says Lightroom 6.1.1/Lightroom CC 2015.1.1 pretend it says Lightroom 6.5.1/Lightroom CC 2015.5.1)
Thank you for this, a useful reference for future instances.
It turns out that the update itself likely wasn't the problem, only what it caused. It embarked me on a lengthy process to remove LR, reinstall it to an error with C++ libraries, to uninstalling these, updating the system, reinstalling them, trying LR again just to find out it has the same problems. Updated the video driver and some more system files, crippled the system boot (a motherboard incompatibility with the latest Windows updates) and reinstalling LR for the 5th time (all along fresh, without preferences), just to come back to the same problem. THEN I thought, why not try to create a new catalog and, voila, that was the problem. Somehow the catalog got compromised with that latest LR update. Starting a new catalog got LR back to work normally. Still reluctant to go to the latest update, for now I'll be running 2016.6.5.1. for a while...
Now I know what to try next time before uninstalling anything. :-)