IMHO, that (2007) postgresql-'gotchas' webpage is not very useful anymore: almost all of these so-called 'gotchas' were relevant only to pretty old versions of Pg.

Here is a list of release dates:

pg version 7.4:  2003
pg version 8.0:  2005
pg version 8.1:  2005
pg version 8.2:  2006
pg version 8.3:  2008
pg version 8.4:  2009

Running a version older than 8.3 is rarely necessary.

Re: comparison PostgreSQL - Oracle: important things that are missing or not good enough in current (=8.4) postgresql:

• Replication: there are (good) replication solutions, but all are outside projects. Version 9.0, scheduled for later this year, will contain native replication.
• In-place upgrades: Upgrades need a dump and restore - and not all databases can afford that downtime. (Version 9.0 will probably have an in-place upgrade facility.)
• Partitioning: possible, but limited to a few hundred partitions.

Then again, compared to Oracle, PostgreSQL is much more immune to over-deployment ;-)

Update (2012.10.27):

PostgreSQL now has native replication (both asynchronous and synchronous (it cannot do synchronous multimaster).

In-place upgrade is also now provided.

Partitioning remains a somewhat weak point. (although it works well enough for many common scenarios)

Update (2018.10.27):

PostgreSQL 10 has logical replication (i.e., you can limit replication to only the necessary tables)

PostgreSQL 10 has much improved partitioning.