Great place to stay in...

Liked: Location is right in airport easily accessible to trains and terminals. Breakfast was good and staff there very nice. Room was small but comfortable.
Disliked: The front desk staff was very cold and spoke down to us like they were scolding us. I felt like they were put out by our presence. They could use some retraining in basic customer service skills - maybe that's just the german way. My wife and I just blew them off and didn't need anything else from them, but just be aware. Would have been a 8 or 9 otherwise.

Perfect place for an overnight...

Liked: Very convenient location if you need to spend a night at the airport between flights. It's located right on top of the train station a walking distance from the terminal. The room is comfortable, and the restaurant is decent.
Disliked: A bit too expensive

Exceptional

Superb

Very good

Bad value for money, not...

Liked: Very convenient location, 10 min indoors walking to the airport. Access indoors to long-term parking for the car (not included in the price). Very clean and comfortable room. Completely isolated from noise, even though our window faced the airport and the highway. Room service lady was very friendly and thoughtful.
Disliked: Very expensive for such a small room facing the highway. The small bed for our kid was not prepared in advance, as it was a sofa-bed. Restaurant too expensive. Corridors were too hot (air conditioning).

Very good

Good location for trains and...

Liked: We stayed at the airport location. The staff was very helpful and friendly. Location worked out great for us to catch a couple of regional trains for sight seeing in Heidelberg and Mannheim. Great location to stay at prior to leaving on our flight home.

Exceptional