On the assumption that one has an uncontaminated backup, at least with a Mac, just trash the new version, (simply drag the Lightroom application icon to the trash), then copy the old, 2015.10 release back onto the boot drive. I've not seen anything in the release notes that makes upgrading essential for most of us.
True ... it is easy enough to backtrack and relatively few users would be in dire straights by sticking with a prior version ... but ... which version of bugs or workarounds are we supposed to revert to? There are some with each release.
What of the user who recently purchased one of the newly supported cameras that were brought into the fold by this recent update that were hoping to finally get off the DNG conversion workaround? when these issues have become so commonplace for the past several updates where does it end?
Don't we users deserve more forethought and consideration? After all, if we as CC subscribers MUST share our monetary support month after month, year after year, from here to eternity ... shouldn't Adobe be expected to hold up their end of the bargain? Why does only one side of the equation receive a pass for their failure to hod up their part of the deal?
I have been in business as a self-employed photographer/graphic designer for over 40 years. Over those decades I have had issues and mistakes. Some of my own making. Some the fault of others in my employ or that provided service to me. In all cases, I was the one who had to make it right with my customers. I had no alternative but to accept the responsibility for the mistake and make it up to my clients. If I didn't, they could quite easily seek out other options. I just don't get why Adobe should get more leeway than any other business.
Ideally, if Adobe insists upon such a lackadaisical pre-release testing policy, it may be much more wise to issue new camera RAW and lens profile support updates separately. I doubt that including support for the new Sony A9 cause the TAT code to break.