I stayed here for Documenta when it was quite hard to find a room in the city. The pluses about the hotel - the rooms are large, clean, and the beds extremely big and comfortable. The lounge areas are groovy and comfortable. While not especially close to the city centre, it is easy to get into the centre by tram c.3 mins from he front door.
The hotel breakfast was OK, some good things (fresh fruit, some good pastries) but not up to high standards that I expect in many German hotels.
The negatives - no air conditioning in the room, which was OK in mid-September but in the summer would be very problematic as the hotel overlooks the main train station. So there is a lot of noise at night.
With some exceptions staff were pretty inattentive. When I arrived there was a problem with my Expedia booking. Rather than call my bank the woman on reception said that I wouldn't be allowed to stay unless I paid by cash. To my question of what I could do if I didn't have cash she suggested I would sleep rough (it was a nasty rainy night).
Internet in the room was inconsistent. When I was unable to log onto Skype for a conference call I was given a different code: apparently logging on with the room no. taps into a weaker network. I wish they'd given me this when I checked in.Another receptionist seemed reluctant to provide me with info about Documenta. Only after I insisted did she poinetd to a map on the wall. When I said I couldn't take that with me she finally gave me a map.