So this is supposed to be a more convenient way to label and file emails...? Interesting idea, but I'm not sure I'd gain any productivity from an app like this.

I installed it and tested out, and it just feels messy to me. Gmail already feels cluttered enough with all of the buttons and crap everywhere, and your app just adds to that.

Also, the To Do labels are goofy (Next, Action, Some Day, Waiting On). I think you can come up with something more intuitive and user friendly.

One last thought - is GTD a commonly used term? I had never heard of it prior to visiting your site, and to do some searching to figure out what it meant.