2012-12-13 WP3.4.1 will update without any problem, only WP3.4.2 has the problem below.
Don’t hit the update 3.5 until they fix the /wp-includes/wp-db.php. You will have problems with any scripts or plugins using $wpdb.
problem with plugin WP-Super-edit
problem with date and time display using $wpdb.
get_taxonomies_for_attachments …. menu.php line 67
If 3.4.2 is working, leave it alone until all plugins are working with 3.5
If you accidently hit the upgrade 3.5 button – rename /wp-includes/wp-db.php to wp-db35.php – copy the old 3.4.2 wp-db.php over /wp-includes/wp-db.php, everything will come back.