We use a postgres backend with the pg4wp plugin and wordpress 3.3.2 (Debian Squeeze package). We've had no problem with a multisite installation using the schema site1.wp.example.com, site2.wp.example.com....
We added the MU Domain Mapping plugin for the obvious reasons, so we could map to site1.com, site2.info..., but it's having no effect. When I create the mapping in the Domain tab, it says "Domain add" at the top but no mapping appears in the Sites tab.
I went into the database, and found that the dmtable and dmtablelogins tables have not actually been created.
In the wp-content folder, I have plugins/wordpress-mu-domain-mapping with symlink pointing into the folder for sunrise.php. After the first round of failures, I also created symlinks to domain_mapping.php in wp-content and wp-content/mu-plugins.