My dad used to fly back and forth to Europe in first/business a lot. He told me that he once got upgraded to the Concorde and, while it was a neat experience to do once, he actually preferred the experience on what I assume would have been a 747. He was doing longer trips so the fly to London to seal a deal and head back home the next day wasn't his use case.

(And as I recall it got him in at rush hour rather than just having a nice dinner on the plane.)