I had to go to Bremen for an exhibition in February this year. I was not only surprised to find a lot of hotels with availability but also with fair prices even though an exhibition was on.
After looking at different websites I went for the Atlantic Universum even though I could not find a review here.

I am very glad I made that choice. The hotel is situated next to a nice park and the Universum (a museum) in a very quiet location. The Tram Station is a 5 minutes walk away and trams leave less than every 10 minutes to the city centre and the airport. The tram costs 2.60 € one way and takes 20 min to the city centre and a bit longer to the airport. (A taxi costs about 10 €). The hotel itself was recently built and is of high & modern standard. Friendly staff at reception and in the restaurant, where I had a dinner on my arrival night.
The hotel also offers room service covering the complete menu! Restaurant prices are also very good for nice and creative food (I paid 28 Euro, incl. tip, for a nice 3 course dinner and 2 glasses of red wine).
The room was spacious with TV, Fast Internet access (ISDN access for free), air con and also the possibility to open the big windows and look out into the park.
Bathroom was big enough and very clean with a very good shower.
Would stay there any time again, should I ever need to go back to Bremen.