How many ArcEditor/ArcInfo licenses exist in the world for the sole purpose of basic featureclass editing?
I can speak from experience that it is not easy to "sell" a free RDBMS like PostgreSQL. But a lot of organizations are comfortable with Microsoft and you know they will eventually end up on SQL Server 2008 (or higher). So being able to edit GIS data in SQL Server 2008 with an ArcView license + zigGIS is very compelling (
zigGIS 2.0.2 isn't going to have SQL Server 2008, but it looks like they are heading in that direction. I always thought that zigGIS was a good candidate for this sort of thing.