Yes, I agree. Everything else WriteRoom did for me is now covered by Byword and Ulysses.
As others, noted the transition from Wr2 to Wr3 was a rough one and the point at which I started looking for alternatives.
Tag filtering would be especially useful in conjunction with a library, if you could view search results across files.
Like I suggested here: LibraryView (testing, ideas, and feedback needed) - #54 by derickfay