I know that posgresql has been brought up before and falls into the "not enough people use it" category.
Is there any scope to re-open the discussion at all - especially in light of Oracle's stewardship of MySQL and VMware using PostgreSQL for their database part of vFabric.
More of the world is turning away from MySQL with Oracle's new licensing strategy. Where I work, this has forced us to kick of projects to migrate our online databases from MySQL to PostgreSQL.
Just a thought.
Duncan