A MAJOR advantage of zenphoto over all the other gallery software I've tried is the filesystem model, in which album structure is mapped onto a directory tree (brilliant!). Another strength is the ability to pull user-generated (i.e. hand-typed!) metadata on title and description, etc. directly from photos themselves. This is ideal since these image-specific metadata can be generated and edited by many programs.
These constitute vital advantages over other packages, in that you get the advanced features and speed of a database, together with the simplicity and lack of lock-in of a plain directory tree.
Unfortunately there is no standard for album/directory metadata equivalent to EXIF/IPTC/XMP/etc. It would, however, be possible to overcome this limitation by using a tiny text file in each album (for import only). I believe it was mentioned 5 years ago, and at the time also developers believed the idea was good. Something as simple as:
Title: My Album Name
Description: This is my favorite album, as you can see...
would do it!
This would be a trivial metadata format to target, opening up the possibility for easier import and migration from many other gallery packages without any database magic. The mtime on these files could be checked in the same way other filesystem elements are at present to detect updates. Speaking as someone who has lost considerable metadata from database issues, it would also give users considerable peace of mind to have full control over both their binary media bytes and their metadata.
Thanks for a wonderful gallery package.