The hotel was in an excellent location for getting to the Frankfurt airport. On a Sat am, it took only 20 minutes, door to door. Might be worse during week days.
The size of the rooms, the beds and the breakfast. The SPA area is nice although the decor of the pool is a little kitsch. The distance from the city centre (it's a 25 minute walk) and the fact that they did not clean our room.