As a rare non-negative side on this one, I had my room at the Bristol (UK) Royal Hotel charged in US$, and they gave me the same rate my credit card would have (based on other purchases I made on said card on the settling date). They did add a 2.99% fee, slightly less than the 3% the Marriott Visa would have wanted--and, because the fee was added before conversion to USD, I got the 5 points/dollar on the fee as well as the room rate.