Current productivity tools fall quite short in comparison.
Once I found out how much you can really do with it, I went on a prosetylizing spree and got a couple of friends as well as my little brother into it. Whilst they're somewhat tech inclined, they're by no means emacs geeks, but they got into it after me showcasing and explaining at least some of the features.
Personally, i think that the only thing that's really essential in getting people into it is a tutorial level to it, similar to interactive tutorials for programming languages (I recall a marvelous ruby one from a year or two back, but I'm unable to find it). Org-mode already scales beautifully regarding complexity, and i think the main thing that turns people away from it is that the manual is a literal textbook and only silly people study it back to back. Or that they're using vim and don't want to switch to emacs, but that's not likely the group of people you're targeting.
* Lots of people understandably don't trust an unknown company/person with their potentially secret TODO lists - add dropbox/drive support from the offset. Also means emacs/vim users can hack the files directly.
* "Normal" people like the agenda and wish they could interact with the items from it - defeats the point, but after yipgo was on lifehacker, I picked up a new type of non-technical user who now make up the majority of my users.
* Make sure it's mobile friendly (turns out the editor I chose doesn't work properly on Android, or at all on IOS).
* Possibly a Yipgo 3.0 thing, but people editing at the same time, ala docs, would be great (something I've wanted).
Actually, if you want to get in touch to see if we can combine forces drop me a mail, phil at apiaxle.com. I'd quite like to monetize the service if possible.
My secrets are on an air-gaped fully encrypted PC. Apart keeping everything in my head this is the best I can come with, but it's still not secure enough for my liking, especially since the whole Truecrypt debacle the doubts are killing me.