I have Beta3 running under Ubuntu Gutsy and Wine and haven't detected any problems so far.
1. Install postgres
2. Create a new postgres database user (the -P is to set a password):
createuser -P poker
3. Follow all the steps here to install PT2: http://www.pokertracker3.com/forums/archives/PT2/viewtopic.php?t=24459
(you can probably skip the part where you actually install PT. All the other steps are what is important)
4. Install PT3.
I really love the UI reorganization and all the graphs and I'm excited to try out the HUD on Linux.