So we use MySQL a lot at work. Yes, it has a reputation for just being a toy database, but we get to push it quite a lot. Recently it got better, see the recent MySQL conference slides for some details. The things we like include subqueries, InnoDB and WITH ROLLUP. It's all quite nice really. Also High Performance MySQL" is pretty good and MySQL Cluster is intriguing. Anyway, I like it when software just works...
