EDIT: Okay, must've touched a few nerves there. Sorry. Question was asked in earnest.
On the other hand, PostgreSQL has historically focused on correctness and full support for advanced database features, looking to supplant Oracle and SQLServer. This meant that speed and ease of use sometimes suffered.
Today, though, both databases have mostly caught up -- MySQL has implemented most of the big ticket features that PostgreSQL had for years, and PostgreSQL (especially with the 9.0 release) has gotten far easier to use and tune, and is now as fast (or faster) than MySQL on most workloads.
The heritage still shows, at times: MySQL, even in "strict" mode, still suffers from annoying bugs and mis-interpretations of SQL features. PostgreSQL is still slow out of the box, often needing to be carefully tuned for the best performance.
Disclaimer: major PostgreSQL user and fan here. I've tried to give as objective an answer as I can.
But if you need a single-user database there's SQLite and if you need a free serious RDBMS there's Postgres. There's really no ecological niche for MySQL. It only hangs on because sites like Slashdot use it (and if you have thousands of reads for every write, and do only very simple queries, it is adequate).
Proper implementations of foreign keys are transactions are slower, and many applications really don't need those features. Like you, I disagree with the choice to value speed over correctness, but unlike you I don't see it as an indication that the MySQL developers were idiots or immature.
Or, to look at it another way: if MySQL's such a load of crap, how'd it ever get so popular? It's not for a lack of alternatives. It's because MySQL offered a feature -- speed and ease of use -- that simply wasn't available elsewhere.
Now the tools are MUCH less friendly, but if you come from an Oracle (or probably DB2) world you'll be used to it. While they require more cryptic commands, they do work very well.
There is the replication thing. When we picked PostgreSQL back up this year to play with for a new little system, we discovered that they took one of the formerly external replication systems and it has been put into the tree. This is a very good step, as the replication situation was a big problem for us. Before there were little third party things (based on triggers) that you could take your chances with, and there were paid replication solutions. Having one built in is quite nice.
Other reasons I like PostgreSQL: more data types (MySQL doesn't even have a boolean type), partial indexing (a godsend when you have large tables), ability to use multiple indexes when querying, full-text search and ACID are not mutually exclusive, and multiple procedural languages.
 Oops, didn't mean to make this a reply.
select x from y group by z
That said, plenty Django sites use MySQL -- including some of the very biggest ones -- without issues. So you're really in good shape either way.
They work together to make for happy master-slave replication.
It's worth noting this is database server level. Hot-standby copies 100% of a PostgreSQL instance. If you want to replicate individual databases on a server or individual tables in a database, Longdiste, Bucardo or Slony are still the way to go.