Upgrade 7.4 to 8.1 or 8.2?

We're looking to upgrade from 7.4 - should we go to 8.1.5 or 8.2?

We have two databases; 7.4.6 and 7.4.11 in a master slave config using
Slony. Both databases use the C locale with UTF-8 encoding on unix.

We've dumped and loaded the data into an 8.1.4 database and have seen no
problems with invalid UTF-8 sequences. So we're fairly happy that we can
upgrade to 8.1.5 pretty easily using Slony.

We're really looking for some extra performance right now.

Are the differences between 8.1.5 and 8.2 significant? Is 8.2 more about
speed or new features?

John