Photos completely messes up photo organization that used to be simple in iPhoto (though wasteful of disk space). All photos are lumped together in a timeline instead of being able to shunt them into events that allow for easy browsing. Also Photos was not reliably importing videos, and would not reliably delete imported photos from the card of my Sony camera. In the end I had to move all my photos from this program onto a Windows machine to organize them properly again, and there was a large amount of duplication, and photos from 2013 being listed as 2017 simply due to download time. Also the "upgrade" from iPhotos to Photos caused this brand new MacBook Pro to run extremely slowly - had to reinstall MacOSSierra as a clean install to undo the mess. Otherwise it is very nice to do simple editing without fear of destroying the original, and it is convenient to be able to create a photo book easily from within the program. But I will be now storing my photos just simply in a directory manually.