I've been wondering what are the easiest OW Partners to upgrade on.

As an AA flyer I know that I can't use AA miles/stickers/SWUs to upgrade non AA-metal. However, I also know that some OW partners will let you use their miles to upgrade an AA codeshare on their metal. So with that said, what are people's experiences with this? Fare class restrictions, etc?

I've compiled a list of possible codeshare upgrades based on the various FFP websites, but I would love to have some firsthand knowledge as the rules & restrictions aren't always comprehensive.