I'm now taking Photos for a spin with the Macphun extension for Intensify. I like it very much so far and do like that it gives me local edit capability and that it is a non-destructive extension, not a round-trip plugin creating files all over the place. What I like about the extension model is that it lets people who do things well, like Macphun, add functionality in a best of breed fashion rather than relying on one vendor to do all things well (and no vendor does all things well). I really do hope it takes off because it is, I think, a great paradigm. I'm not a high volume shooter and have never needed terribly sophisticated DAM, though I would obviously like to see it improve in Photos. And ideally, if over time Pixelmator can get extensions in place that are more pixel level, I'd be in heaven.
I like what you are saying here. Indeed non-destructive editing by 3rd party is a very unique value proposition and it has an unfathomable potential, that's what hurting so much that Apple has been so minimalist in implementing the DAM element in Photos.
Worse yet, I had a look at the API for Photos extension and there seems to be only capabilities for photo editing. So no extension on the DAM side, maybe it's the saddest thing and overall after the betrayal of Aperture I see not alternative but to go for LR, and I'll remain emotional about it for a long time...