PostgreSQL is going to be my database of choice for a good long time, I think. I've always liked the way that PostgreSQL sort of forces you to do things right, rather than letting you do things easy (but are bad ideas). For instance, I've never been comfortable with the idea that a blank string constitues NULL. PostgreSQL doesn't let you do that.
I suppose I've been swayed by the Postgres vs. MySQL argument, namely the argument that MySQL wasn't a serious database as it did
weird things way too often, and lacked things like transactions. But, in all fairness, it does what people need it to do, and does so well enough that places like Slashdot use it.