Thanks for the feedback! I will work on improving the UI for single attachments to make use of the Categories/Tags interfaces from the post editing area in a future version of the plugin. It's kind of tricky to get them in there, so I didn't do it for the initial release.

A note on attachment taxonomies in Core: I think the problem is that using `register_taxonomy_for_object_type()` isn't sufficient to get a usable interface. While custom taxonomies integrate perfectly into regular post types, attachments have a custom UI and therefore work differently - and I wouldn't have made a plugin if it had just been for the plain registration of taxonomies.

I understand that Core doesn't want to add these taxonomies by default, but it would certainly help if the underlying infrastructure would support custom attachment taxonomies out of the box. Maybe we can work on that someday.