Alexander Kuznetsov on SQLblog.com
has an interesting series going entitled with Learning PostgreSQL. In the series he focuses on what it takes to move
a SQL Server database and App to PostgreSQL and highlights some of the key differences between the two platforms that you should watch out for.
I recommend it to any SQL Server developer planning to make the switch to PostgreSQL or any PostgreSQL consultant tasked with the job
and not familiar with the intricacies of SQL Server.
The list of articles has a duplicate. It just so happens that I've been writing about why duplicate tuples (rows) are not part of the relational model, and I can't help but think that your list makes a good example for my arguments :-)
I haven't read all his posts, merely searched them for 'optimizer', but I think it's worth mentioning that differences between how the query optimizers work can result in a few rather nasty performance issues, particularly with queries with lots of joins or big/complex views and a few joins.
I'll try to comment on one of his posts when I'll have the time.