SourceForge has been running on a (gulp) pre-beta PG 7.1 for over two months.
He didn't say PG was *better* than MySQL. He said it scaled much better under load testing, due to having row-level rather than table-level locking. He also likes the additional functionality, i.e. referential integrity checkng and stuff like that. But it was the behavior under load that caused him to switch, the MySQL version was of SourceForge was giving them fits with performance.
Though I personally prefer Postgres to MySQL, the reality is that 90% of the sites using MySQL probably don't get enough traffic and are probably simple enough to not be seriously impacted by the locking issue. SourceForge serves up highly personalized pages, with that being driven by the database - you know, all those links to your projects and stuff. Lots and lots of database hits.
