Drizzle is not a valid choice for apps that require things like stored procs and triggers, which they removed. Of course, not every app requires what they remove; MariaDB is a fork by the core MySQL team, if those features are needed and MySQL cannot be used.
I have been writing extensions to Postgresql in C++ recently, and it's amazing what you can do if you have the full flexibility of loading a .so into the db process and doing whatever you want.
I didn't mean to imply that it is no longer a useful or interesting piece of software; just that it is not a simple migration for some project that specifically use MySQL features.
I did the same thing in SQL Server, too, so it's not a new concept and the other RDBMs with that ability still have a use for traditional stored procs.
My experience with both stored procs and running actual programming languages on the database is that one does not replace the other; but I'll wait with an open mind to see.
Official homepage: http://drizzle.org Blog: http://blog.drizzle.org Source code: https://launchpad.net/drizzle