I am running Lightroom Release 2015.7 and Photoshop 2017.0.0 in macOS Sierra 10.12.1 on a MacBook Air. After updating to Sierra, Lightroom began to hang frequently, capturing nearly all CPU resource and requiring a kill to quit the application. I have been sending diagnostic reports to Apple several times a day over the past 3 weeks.
Lightroom hangs most frequently when I open an image from LR to edit in Photoshop, then save and close the image in Photoshop to return to Lightroom, where I may edit (Develop) the image further. The Photoshop application is left running.
I am not encountering problems with other applications.
I would expect there to be some way to report this problem to Adobe in a more formal manner. I tried a chat session; however, the representative wanted access to my system, which is certainly not an option as I hold far too much confidential data.
So, I am making this post hoping that someone in the Adobe organization will acknowledge the problem and at least let me know whether others are reporting similar issues or if I appear to be the only person complaining.