Where can I find information on why I should upgrade from 12.x to the current version (18.x at present), without reading through every point version release notes? Is there something that summarizes each major version? Obviously you get another 12 months of free support and upgrades and some newer/updated skins require newer versions (example jAlbum 17.x or higher). Is there a document with a collection of added functionality by version? Like a "what you are missing out on", by major version?
I don't think anyone is going to take the time to summarize the release notes for you. The material is all there. There are countless new features and major performance improvements, along with a long list of bug fixes.
And if you want to use most of the current skins, you'll need something newer than jAlbum 12. Laza's skins all require at least jAlbum 14.1, AndreWolff's skins call for jAlbum 15.3, and mine are now all being compiled to jAlbum 17.
If you want to quickly find just the new features since version 12 you could open the erase notes page and search it for ‘new’. It will find a few false results but it is quicker than reading all of the posts between 12 and 18.
If you do upgrade I’d recommend deleting the ffmpeg executable to ensure you have a more recent version of it, see the yellow note on this page
I think it's a valid question. The first entries listed for each new major release at our release notes page will give you an overview of the most important improvements, but our blog presents some of these improvements in a more digestible way. Here's one summary blog post I still highly recommend if you're at v12: