Amex has also always sided with me as well. Even on one occurrence Amex talked with the merchant and was going to side with them. It was a doctors office visit, and what happened was that I paid my co-pay but they insisted on billing me more. Amex told me that I signed the CC receipt and I stated that yes I did because I could not dispute it with them (they were morons and wouldn't budge). I did not want to get sent to collections and have my credit ruined, so I paid and now I'm dealing with you guys on it. The CSR basically said ok, we'll "goodwill" this and remove the transaction. If you're a good enough customer and you have a legitimate side of the story, they can side with you.

Any other disputes I've had they removed without question.