I stayed here for two nights in September, arriving by train late one evening and leaving early 2 days later. When I arrived the reception was closed but there was a clear sign on the door, explaining how to collect the room key (from the bar round the corner). That worked no problem, though I had called the hotel earlier in the day to tell them I would be late.
Again with my early departure (train at 07:00), I talked to the manager who was most helpful and said that although breakfast was officially only from 07:00, she was there from before 06:30 and there would be no problem to be down then.
The hotel is ideally situated for Karlsruhe station, just across the station square, literally 2 minutes to the station platforms. It's very functional, but spotlessly clean. I had booked a single room and actually got a room with just a single bed, but it was quite decently sized and adequately furnished.
Breakfast was a generous buffet and if the weather is OK, you can sit outside on the rear terrace overlooking a beautiful park.
It is a little noisy, even at night, because of the trams on the station square, but I still managed to sleep fairly well.