After years of using MySQL and other databases, I decided to certify my skills. I originally learned DB development on Oracle 8i and shortly after added a parallel track using MS SQL Server to accommodate a client with an MS-based application.
Some time in Y2K I added MySQL 3 to the repertoire. The experience was like learning to drive on an 18-wheeler and then getting into a Geo Metro.
Now, years later, I am quite pleased with MySQL thanks to the advancements which include most of the features that are required for enterprise-level web development. Everyone talks about the addition of transactions, but I feel triggers, procedures and functions are an inseparable part of any DB, not to mention the most important MySQL improvement that came with InnoDB tables- foreign keys that actually maintain referential integrity!
The upcoming versions are slated to include some nice additions to look forward to such as useful cursors (as opposed to the current read-only forward-only cursors) and a built-in cron for scheduled events.