Been playing around with this for about a week, and it's brilliant. My phone's photo album has become a jumble of life photos (read: my dog) that I WANT to show people, interspersed with dozens of "reference" photos (as Danny aptly put it) of whiteboards, slides, sticky notes, random inspirational ideas etc. that only I care about - they all get buried and have cluttered up my entire photo album (honestly, Apple's folders have zero organization and are a massive pain to use).
Getting all those photos OUT of my album and into Birch has 1) made it so much easier to find and browse my reference photos, and 2) has liberated my photo gallery. Definitely recommend giving this a shot, and can't wait to see how it evolves.