Hot on the heels of the Announcement of the second 9.1 Beta release there are now packages for it in Debian experimental and backports for Ubuntu 10.04 LTS, 10.10. and 11.04 in my PostgreSQL backports for stable Ubuntu releases PPA.
Warning for upgrades from Beta 1: The on-disk database format changed since Beta-1. So if you already have the beta-1 packages installed, you need to
pg_dumpall your 9.1 clusters (if you still need them), and
pg_dropcluster all 9.1 clusters before the upgrade. I added a check to the pre-install script to make the
postgresql-9.1 package fail early to upgrade if you still have existing 9.1 clusters to avoid data loss.