Are you aware of the DEFINITIVE analysis of outliners and PIMS on the web:
http://john.redmood.com/organizers.html
This is THE place that people look (IMHO) for info on organizers. This link comes up a LOT amongst people looking for this sort of solution.
I recommend you try to get your app listed there (perhaps it is already, haven't looked in a year).
Also, you may find some very good analysis of what's needed in an info manager.