Testing the upgrade from Pg 7.4 to 8.1. The upgrade itself is a bit ackward, but made easier by Debian's cool
pg_upgradecluster utility. Giving the DB a whirl... it's fast!
Using one of my devel instances of Moodle -- which has a copy of last week's production DB (45K users, 6K courses) it feels much snappier than 7.4.9. Until I've seen more, I'll blame it on the fact that I've just done the migration so all the database must be in memory
(Actually, I don't know if any changes in 8.x have a negative impact on performance -- OTOH, some things like max() and min() do get a significant speedup.