I have a few posts on doing it with 9.3. The first is here and you can get to the rest of them from there: http://geobabble.wordpress.com/2008/05/28/using-arcsde-93-with-postgresql-part-1/
I've done it once with 10.0 and have had no issues. I will say that, when using PostgreSQL and PostGIS with ArcSDE, that I strongly recommend sticking to whatever versions are supported by Esri.
