Spoken as a true programmer ... as in, someone who isn't a DBA. The SQLite DBMS is a great toy. It can be a useful development aid. But, unlike a RDBMS, SQLite doesn't enforce relationships, types, or anything that one would need to ensure data integrity. It doesn't have transactions (ACID or not), proper indices, and a lot of other stuff. In other words, the moment your application started being real, SQLite would do anything from fall over immediately (best case) to corrupt your data without you knowing it (worst case).

While I prefer MySQL (using the InnoDB tabletype only), PostgreSQL, Oracle, DB2, Sybase / SQL*Server ... anything that's ACID-transaction compliant, provides proper foreign keys, indices and the rest of it is necessary for a proper application. This isn't optional.

The rest of what you said - the WUI thing is a really cool concept that I think I'll be grabbing. But, data is the foundation of an application - treat it properly or it will beat you senseless.