I just used the "Upgrade Reservation Using Miles" function on Continental.com to upgrade an EWR-CDG B fare to BusinessFirst, and it gave me the upgrade for $0 and 0 miles! Never had to enter my PIN or select a method of payment.

When I look at the reservation, it appears that it was indeed upgraded to F. I'm wondering now whether or not I should call Continental to beg them to take my miles and $$$...