[At_Libitum]

apart from the fact that some don't see the benefit of multi-file editing (as opposed to a cumbersome save-close-open- series of repeated steps), TextPad is not exactly multi tab, but it does allow switching between 'files' rapidly, you just flip through them as in a book, one 'file' a page. Plus you have your 'files' listed in a panel to select one directly.

and for more styling options there's Nocs, which supports Markdown and is dropbox enabled