Until recently, MySQL in my opinion was a good RDBMS to develop on, make some prototypes and then carry your schema over to a more mature RDBMS such as DB2, Oracle or SQL Server. It lacked certain features, that I considered as “givens” in an RDBMS solution, such as triggers, transaction support, views and even the dreaded stored procedures (An article will follow on this in the future).
However with the release of version 5.0, many of these short comings have been addressed. Views, limited trigger support, transaction support and stored procedures have been introduced. This, in essence, completes the offering and finally puts MySQL in the same category as the big boys.
The MySQL Effect The biggest impact MySQL has had on the RDBMS industry doesn't even have anything to do with the software. Its the fact that with a stable, full featured Open-Source RDBMS solution making waves, it has forced the big 3 to release free versions of their previously extremely expensive software. Oracle, IBM and Microsoft each released free versions of their software to the public. This in hope that as you get used to one product, and your business or needs grow, you will scale to a paid version of their products.
Conclusion MySQL is a good piece of software, well thought out and free. However, lets no kid ourselves. Oracle, DB2 and SQL Server are mature database offerings with many more features that MySQL. MySQL is still playing catch-up to the big 3. However, its doing a good job of it. As for whether to use it over any other solution? I guess it falls under the IT religion thing. If you sweat and bleed Open-Source, go for it! However with the release of free versions of the big 3, you will have a hard time convincing me to use MySQL over those.