The 1.3 release now uses a more polished database solution than the one I had previously cooked myself: it’s now using http://www.sterlingdatabase.com/. Hats off to these guys for filling the gap that Microsoft left by currently having no local database API on the phone (1), unlike Android and iPhone which have SQLite APIs (2).
Sterling’s a lot easier to use than SQLite as there are no SQL statements to learn, you just use Plain Old C# Objects (POCOs), which I was already using in the WordLive code. From there you can use LINQ to objects to query your database.
(1) The next Windows Phone platform update “Mango” will have database support and this was discussed at the Mix ‘11 conference – http://channel9.msdn.com/events/MIX/MIX11/DVC12