I have all these certs from the west coast promotion. The certs are good with most fares, and there are no restrictions on upgrades. I am now trying to book travel to London. UAL.com gives me this when I plug in the e-cert while looking for upgradable fares:

"Promotions and upgrades may not be combined on united.com. Please continue your search using either your promotion code or upgrade"

Web support suggested that I buy the ticket without the discount, then they would issue a credit to my card. Sounds backwards to me.