My opinion/sense is that Postgres is better in every way, except replication. Which ironically makes it far worse than mysql since you can't easily use it for huge datasets.
Not to mention, that MySQL replication is known to be horribly fragile, and silently corrupts data -- which is why you need separate tools (like Maatkit) to know when it's time to rebuild the slave.
It's a feature.
It seems like almost every time I've read a review of a database book, there's been somebody complaining that it's "full of a bunch of boring theory" (or else, "at least this book doesn't have much boring theory"). At the same time, some programmers nonchalantly do things that could land them on a DBA's equivalent of The Daily WTF (e.g. http://ask.metafilter.com/117908/Theres-got-to-be-a-faster-w...). It's a weird disconnect.
/me apologizes for the rant.
I haven't used PGCluster, but it's synchronous multi-master and thus inherently fails to scale out as well as async systems like Slony-I and Londiste. Probably great in circumstances with only 2-3 db boxes though.
Londiste, on the other hand, is awesome, and with the 3.0 release now has hot backups. Simple to administer, rock solid, and has really important features like live DDLs. Demand Londiste and the SkyTools package! Don't settle for less!