To me, the difference on appreciating a hotel are the services.
This guys are really customer-oriented. It was no problem for them to wake up 5 AM to prepare the breakfast and take me to the airport with their shuttle. And the shuttle was included in the already low fare. What else can a traveler want?
I really recommend this hotel for catching an early flight from Cologne airport.

This friendly, family-run hotel is close to the motorway, which suited us perfectly, although it's in a suburb, rather than central Cologne. Our room was bright and airy, with a balcony overlooking the garden. The place had a very comfortable and relaxing feeling to it. The proprietors were so friendly and welcoming, and made us feel really at home. Breakfast (continental style, but with eggs prepared to your preference) was served in the pretty, sunny dining room. The hotel is just off the local high street, where you can find a range of restaurants (although we liked Ristorante Antica Roma so much we went there all 3 nights of our stay!)

The owner and her staff makes this hotel a very nice place to stay. We arrived in car - and if you do not use the gps - it can be difficult to find as it is placed in a resident quater with one-way streets. However, when your are there you feel at home.
The owner, Mrs. Frieden gave us excellent, practical advice on buses, trams and S-Bahn connections to airport and to visit Cologne and the next morning she took us to the airport in the shuttle-bus. Thanks for your excellent service and nice approach.
The hotel is not new, but things function, rooms are well equipped and the breakfast buffet is excellent (including fruit).
For a stayover between flights and if you accept not to live just under the Köllner Dom this is a fine place to stay.

We stayed at the Karsten for one night in July 2008, and when we then decided to come to Cologne for the Xmas markets (6 of them) in December 2009 there was no doubt, We WOULD be stopping here again! We didn't use the Airport shuttle service as we took our car, (free parking) we did use the free wireless internet (ask at the desk for an access code) We did love the Breakfast every day, (What a spread). We did use the park-and-ride train station 1 mile away to get into the City, 2E40 for about 10 miles, very quick and clean trains. Anna and her staff genuinely enjoy running this hotel and it shows in everything they do. B&B only, but they are surrounded by restaurants of most types.