Has anyone experience filtering the media library by tag or searching by tag (native Umbraco categories) or any other properties (other than file name or node name) for that matter?

Are you infering facet searching in examine? Search extenstion might help? https://github.com/callumbwhyte/umbraco-search-extensions#facets

Thanks @Mike Chambers I wasn't sure if this was an extension or something coming to core. I will have a read.

I think the new search abstraction has facetting... umb dev rel deepdive had an episode on it... (but not till v18?)