If you're going to put up source (or in this case, XML), may I suggest two things?<p>(1) Please indent.<p>(2) Consider syntax highlighting. <a href="http://softwaremaniacs.org/soft/highlight/en/" rel="nofollow">http://softwaremaniacs.org/soft/highlight/en/</a> will do it for you.
Have you found any significant increase in users from the "discoverability by being in the Microsoft App Store"? Also, any reason you didn't implement this as a classic COM plugin?<p>We wrote similar apps for Outlook 2013, but didn't see much traction. Also, compared to classic COM plugins (which are also still supported by 2013), the API is very limited. That combined with no backwards compatibility makes me think that it would have been better to implement this as a COM plugin for better coverage and functionality...