There is another new feature in 9.2 that doesn't get much press, and probably because it's hard to explain. It is a pretty useful feature if you are working with the new json type or the existing hstore type. In prior versions if you used a subquery and converted the rows to hstore or json the column names were not preserved. Andrew mentioned a back-port path for this issue in Upgradeable JSON. We described a workaround for this issue in Mail merging using hstore. The workaround for including PostGIS geometry in json record output as described in Native JSON type support wouldn't work as nicely without this enhancement. Here is an example to demonstrate.

CREATE EXTENSION hstore;
CREATE TABLE clients(client_id varchar(5) PRIMARY KEY, contact_name varchar(100), business varchar(100));
INSERT INTO clients(client_id, contact_name, business)
VALUES ('DCH', 'John Dewey', 'Dewey, Cheetham, and Howe'),
    ('IYS', 'Spencer Tracey', 'Investigators at Your Service'),
    ('ABC', 'Abby Back', 'It is all about ABC');
    

SELECT client_id, hstore(c) As data
FROM (SELECT client_id, contact_name
FROM clients) As c;

If you were running the above query in 9.1 or lower, you'd get this which as you can see is not ideal:

--9.1 behavior
 client_id |                data
-----------+-------------------------------------
 DCH       | "f1"=>"DCH", "f2"=>"John Dewey"
 IYS       | "f1"=>"IYS", "f2"=>"Spencer Tracey"
 ABC       | "f1"=>"ABC", "f2"=>"Abby Back"

If you run the same exact query in 9.2, you get this much nicer output

--9.2 behavior
client_id |                         data
----------+------------------------------------------------------
DCH       | "client_id"=>"DCH", "contact_name"=>"John Dewey"
IYS       | "client_id"=>"IYS", "contact_name"=>"Spencer Tracey"
ABC       | "client_id"=>"ABC", "contact_name"=>"Abby Back"