Is it just wrong implementation in Opera and Weston Ruters' JavaScript that empty select value ignores by validator? If so, I think that it should be clarified in specs.
See test page and further explanation here.
Update: I see now that there is no required attribute for select in specs.
Probably this should be corrected to allow required attribute for SELECT. In most cases SELECTs have first option blank or "please select" with no or empty value, so SELECT needs validation.
Also consider to make invalid (if field is required) check boxes and radio buttons with empty value. It may be helpfull in some cases.