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These little puppies [postgresql.org], i.e. recursive queries, look pretty cool too. Sounds like a good tool for threaded comment systems or finding related items in a table:

Recursive queries are typically used to deal with hierarchical or tree-structured data. A useful example is this query to find all the direct and indirect sub-parts of a product, given only a table that shows immediate inclusions:

WITH RECURSIVE included_parts(sub_part, part, quantity) AS (
        SELECT sub_part, part, quantity FROM parts WHERE part = 'our_product'
    UNION ALL
        SELECT p.sub_part, p.part, p.quantity
        FROM included_parts pr, parts p
        WHERE p.part = pr.sub_part
    )
SELECT sub_part, SUM(quantity) as total_quantity
FROM included_parts
GROUP BY sub_part

... It will take a while to wrap my brain around this new concept though. That doesn't look like a normal query I'm used to reading!

They'll get replication some day soon. But there is a lot of cool, very useful stuff with every new release. I usually feel like kid in a candy store wondering what's new that I can exploit.