I'm the designer of SQLNotes (code name) so I'll gladly answer. I've been meaning to start a SQLNotes thread, so thanks to you superboyac !
The ideal information management app must be an excellent outliner with multiple parents support (when required), an excellent linker (i.e. like the web), an excellent tagger, an excellent editor supporting rich text editing in the outline AND in a second rich text window, support flat and tree-structured display with or without a data grid, usable as a flexible database supporting user-defined fields, calculations (both equations and user-defined functions), reporting and an have excellent search engine. Finally, it needs to have a customizable UI, support drag-drop and have links to all other major apps. Idealy, it should be able to pull information from external sources as well.
IMO, ALL these features are required to adequately organize all kinds of information (not just a specific kind of information), and this for just about any user.
Ecco is/was an excellent outliner+data grid, but had no item to item linker, and forced structured tree representation, which may or may not suit the specific information or the way a particular person wants to work/organize its information. It had rich text outlines and customizable UI but for the rest, the above features were not great or not there at all. Specifically, it does not have an editing pane (i.e 2nd pane).
As for 2 panes outliners, zillions of them, they lack the data grid to enter useful data in the outline so they are mainly good at text editing (i.e. reducing the number of word processor files). When the outline only represents text, a grid is not necessary, but when numbers, categories, notes, etc are required, a grid and a properties pane is a must. None can perform calculations (neither row nor column calculations) and data analysis.
Finally, no other product I know makes its data available to other apps. SQLNotes data is accessible to all Office apps and other suites (through ODBC links). No one want his or her information locked in a program. Exporting is just not enough nowadays.
SQLNotes has ALL of the above features.
SQLNotes development started 4 years ago. As a flexible database/ouliner/grid it is being used by a number of companies for more than 3 years. It is now in beta tests as a PIM (actually closer to alpha stage). It takes the best of Ecco, and improves upon it, taking the concept much further.
The current beta available at www.sqlnotes.net
is very stable. You are all welcomed to download a free copy.