I finally got around to adjusting my SQL comparison page, so that the improvements in PostgreSQL 8.4 are taken into account. PostgreSQL is now standards-compliant in the sections about limiting result sets; actually, PostgreSQL is the first DBMS that I know of which supports SQL:2008's OFFSET + FETCH FIRST construct for pagination. PostgreSQL's new support for window functions is also very nice.
My page doesn't cover common table expressions (CTEs) yet, but it's certainly nice to see more and more DBMSes (including PostgreSQL, since version 8.4) supporting them. Even non-recursive CTEs are important, because they can really clean up SQL queries and make them more readable.