I certainly enjoyed my stay at Kongresshotel, but I kept finding things that made me think "damn, if they just changed this detail everything would be a lot better!"
Good cop: The area where they serve breakfast is very very beautiful (Restaurant Granada, on the lobby floor) and the breakfast is very good as well. The new rooms ("Relaxing") have a fantastic bathroom with a huge glass window toward the room. This gives a feeling that the room is bigger (and it's spacious enough in the first place). LCD tv was nice too. The hotel staff were happy to help, room service was excellent and the Granada restaurant had good food (moderately priced). Room light design was very good too, it made you feel comfortable at all hours. Good amenities. Shampoo bottles (rare in Germany, they usually just screw a shampoo bottle onto the bathroom wall), slippers, very nice bathrobe, goodnight Haribo, afternoon snack.
Bad cop: they need a better elevator! First of all: it's slow! It was slow enough to bother me in a 6 floor ride. Plus, the doors and buttons look ready to fall apart. Not a real problem, but I can't believe they don't spend a little money to make it look as good as the rooms. Also: as always in germany... internet! 13euro per day?!? Come on, that's paranoid. Everywhere in the world you can find hotels with free wifi, or at least with cheap wifi. However, that was a problem in every hotel I've visited in Germany, so I won't take it into account. Glasses for the minibar were clean but looked as if they were placed there two weeks ago.
Anyway, the only serious problem I had was sleep. I'm not an easy sleeper, so these may not bother you at all, but anyway here's what bothered me:
a) One pillow type - and not a good one. I actually *never* ask for specific pillow types at all, but when you only have one type it should at least be a medium thing: not too hard, not too soft. They had only extra-ultra-uber-mega-soft pillows.
b) Heating. This was the main thing actually. There's no temperature control system, so you just try to get the room warmer or cooler by turning the heating from hotter to cooler. That doesn't work well. I found myself waking up in the middle of the night because the heating had decided to suddenly interpret my setting (which 2 hours ago gave me moderately warm air) as "make the air boil" and then when I would lower it to a normal temperature I'd wake up an hour later finding out that the supplied air was icy. A setting of "12 o'clock" on the rotary switch doesn't mean that air is supplied at a specific temperature. It means "not as hot as 15 o'clock and not as cool as 9 o'clock". But these values are not specific either, so what at first was "warm" can become "extra hot" or "frozen" later. Seriously if there's one thing they really need to change, that would be this.
c) I booked a double room for single use to have a more comfortable bed. Instead I found two beds stacked next to each other. Yep, it's not the first time it happens, but it's never good.
d) there are no window blinds and the thick curtains don't completely shut the light off, so I found it hard to get an afternoon nap.
Overal, I enjoyed the room very much, it was comfortable and really nice to hang out in, but they just desperately need to install a better heating system.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.