I have been using NoteTab since the late 1990s. I created a simple, in-house text tagging system (clipbook library) for editors at the publishing company where I work, and moved them from editing manuscripts in XYWrite (ugh!) to editing in NoteTab Pro. I wrote filters for Ventura and later Quark so that the tagged text files could be imported properly.
I am now starting to work on an iteration of the original library, to tag manuscripts for both print and ebook (ePub) use.
I also use NoteTab Pro heavily for simple XHTML coding, relying on TopStyle for stylesheet work. I use UltraEdit Professional for other coding work and very large projects.