I looked into Sort Shots after you mentioned it and it certainly looks appealing. Unfortunately the reviews were not that good as a significant amount of people complained about the app crashing regularly. It's possible that was fixed in a newer version though. It's a bit of a shame that the built in Photos app isn't more robust. It should at least have better album management if not full blown metadata editing.
I recently caved and purchased Filterstorm Pro, mainly for the RAW support and Lightroom/Aperture like editing features. It is a classy piece of software although a little pricey at $15. I've not had a chance to do much with it yet other than some sample edits but it seems to have a fairly robust library capability, supports multiple versions of photos, and various ways to transfer. It might be worth looking into for people seeking more Pro oriented features.