Sandman
So I installed the beta of the OSX Photos app, and opened my iPhoto/Aperture library with it, which worked just fine. Then I went into preferences to enable iCloud Photos, which was the entire point of OSX Photos. And this is what I see:

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Yeah, that's right, you can't used referenced photos if you want to sync with iCloud, you have to keep all photos inside the library, totally managed by Photos.

Which of course is a problem, since Photos isn't a professional tool, and most of these photos need to be available to Lightroom. If I consolidate them into the library, my entire Lightroom catalog will crumble and die.

It seems that this Photos thing is always on the edge of a good idea, but then a deal breaker comes along... :/

MC
It is Apple so what do you expect.