I seem to remember that each of the following three statements worked in PG 9.0. Is the last one failing expected in 9.1? Or is it due to the various contrib modules I've been playing with? (I've installed btree_gin, btree_gist, semver, temporal, pgcrypt, spi/timetravel, and a couple more I can't remember off the top of my head...)
test=# select row(1,2) = row(1,2); -- returns t
test=# select row(1,2) is distinct from row(1,2); -- returns f
test=# select row(1,2) <> row(1,2);
ERROR: could not determine interpretation of row comparison operator <>
LINE 1: select row(1,2) <> row(1,2);
^
HINT: Row comparison operators must be associated with btree operator families.