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.

Sandman
I've had very low expectations for Photos, but Apple did release Aperture, which is by far the best photo management app to have ever existed,

so it's not like they can't do it.