I havent stayed at the Courtyard, but I did recently return from a trip where I stayed at the regular Mariott. It is almost right across the street from the Messe and various forms of clean fast public transportation that to me were even better than most airport shuttles I've been on. It is still a little bit away from downtown frankfurt, but for a few Euros you can use the public transportation very and go anywhere (including airport) very easily. The hotel itself was nice too, but nothing exceptional. Unless you need to stay at the Courtyard for some reason, I would recommend the full-service Mariott. Let me know or search for one of my threads about it if you decide to stay there and need directions, etc...