I started testing 3.5 with hyperDB installed as well. I’m getting the same results as carmelosantana.
Notice: Undefined property: hyperdb::$dbh2host in /usr/local/export/wordpress/wp-includes/wp-db.php on line 575
Notice: Indirect modification of overloaded property hyperdb::$dbh2host has no effect in /usr/local/export/wordpress/wp-content/db.php on line 604
