Looks promising. Some suggestions:
* on my set-up the help window is slightly off the screen, and it doesn't
have a "close" button.
* the notation for keystrokes (M-X) is not intuitive
* it would be useful to have line number display and "goto line", as XML
parsers display error messages in terms of line numbers
* it would be nice to have an option to indent to show nesting (either for
display on screen, or a permanent transformation of the file). Or better
still an option to collapse and expand nesting levels.
* Right-click on a tag would be a more standard user interface than "tab" on
it.
* There are many "familiar" features like double-clicking on a word and
drag-and-drop missing.
Mike Kay