Amex leadership clearly made a misjudgment about Costco keeping their card as the exclusive card for Costco. It was a dumb error, but I agree with the judge they shouldn't liable to being sued. If every corporate decision was open to suits like this, the courts would be a mess and corporate decision making would grind to a halt.
On the other side, I was glad to see Costco drop their card. I oversaw the accounting at RAD for their card and they charge the retailers substantially more than other cards. These fees reduce the retailers profit margin as the retailer has to pay it.
While I have friends who love the AMEX card, I don't care who provides me with short term credit. Yes, I am sure there are benefits to having an AMEX card, but I am not going to pay AMEX to have their card. Their loyal clientele love the prestige of the card. Different stokes, different folks!
I would prefer to have the annual fee they charge in my own pocket - not AMEX's. Clearly, Costco felt the same about the per transaction cost. As a Costco shareholder, I LIKE when Costco gets rid of these unnecessary expenses!