[jacques_chester]

For me personally:

1. MySQL's "feature set" is usually described as a union of storage engine features; whereas in fact you only ever get some of them at a time. I find that extremely annoying.

2. PostgreSQL has a decent, smart query planner. In cases where I have multiply-layered views, I've seen MySQL throw up its hands and manually churn through each view in turn, while PostgreSQL did the smart thing and combined all the views into a single execution plan.

3. It's much more featuresome for in-database programming. The web world tends to look on RDBMSes as flat files with a funny accent, so this doesn't matter for a lot of programmers. But sometimes you absolutely must either a) protect the data or b) place computation as close to the data as possible. Featuresome databases like PostgreSQL, Oracle, DB2 etc let you do this. MySQL not as well.