Oh happy days. Denver FSDO did not have any problem with my CAA medical (just copied the deatils from it) and nor did the school in Colorado where did my FR and rented a C-172. they just wanted to see my "Temporary Airman's Cert"
Other people's experience sounds like a problem I had with the Greek's in Crete (their authorities not the flying school) where they categorically refused to acknowledge the existence of the JAR and insisted no Greek License ... no fly.