Matt has been writing about SharePoint "lock-in" for years. Partnering with Ingres, which prides itself on a truly enterprise class open source database (it's based on PostgreSQL), gives it a leg up on competing.
Ingres currently offers an installation bundle for both its database and the Alfresco ECM (Enterprise Content Manager). The bundle contains the Alfresco 2.1 and the Ingres 2006 Release 3 community editions.
The new offering is what is called a "software appliance" combining the two capabilities, up to date and enterprise ready, supported by Ingres for $32,500 per supported server.
The market is fairly limited. The Alfresco ECM already supports Office. If you buy Matt's fear of SharePoint lock-in, and you have an Alfresco license, you may already be good to go.
It's the database fans who should prick up their ears. Ingres is not only seeking to keep you out of Microsoft's clutches here but make sure you don't get into Sun's, owners of mySQL. Getting into your pocket through content management is the play.
So you can have a big boy database and big boy content management with Office-compatible files, without becoming one with the Microsoft borg. With open source.