Rather than a review, here's the complaint letter I wrote:

Dear Sir / Madam,
I had the misfortune to stay at the Holiday Inn, Cologne-Bonn Airport last week, checking in on Monday 10th November and out on the 11th. I stayed in room 312 and paid €183 for my room and breakfast. My invoice number was XXXXXXXX.

In short, I was absolutely appalled at this hotel, expecially given the high price I paid for it. Specific compaints include:
* The room was very shabby and was in dire need of redecorating.
* The bed sheets were hard and of very poor quality.
* The pillows were old, flat and smelt bad.
* The bathroom design was terrible. When sitting on the toilet, the dirty toilet brush was digging into my leg. This was extremely unpleasant.
* There were no tea and coffee making facilities in the room.
* There was no iron or ironing board.
* The toilet paper was cheap and hard.
* The shower curtain was extremely dirty.
* The shower had jammed and was very hard to turn on and off.
* The minibar choice was very poor.
* The air conditioning made a noise, but no noticable difference to the temperature of the room.
* The barman was allowing people to smoke in the bar. I believe this is against the law.

At least the staff were helpful. Sadly, although they were helpful, they didn't have much idea of what they were doing most of the time.

In my years of travel, I have not found such a poor hotel at such a high price. Had this hotel been €80, then the standard may have been acceptable, but at €180 it is wholly unacceptable.

Generally well run hotel, efficient pick up from the airport, helpful reception staff, nice clean spacious room. Good breakfast.

No tea/coffee making facilities in room however. No free mineral water in room. No hotel pool.

Generally absolutely fine but at the 160 Euro that I paid plus charges for breakfast plus charges for Internet, it just seemed overpriced to me and taking advantage of the fact that there is not much competition near to the airport.

The hotel is well located, a few km from the airport. You should only stay here if you are taking a late or early flight at Bonn airport.
Rooms are small boxes. For the high prices they charge (over 160 Euros per night) that is extremely expensive, even by European standards. So with rooms too small, a tiny TV, and an equally tiny toilette, this means that you should only stay here if you have no choice as a consequence of your flight schedule. If so, there is no reason against staying here bearing in mind that this is a modest 3 star property with 4 star prices.

nice, functional airport hotel. We arrived at 1am and hotel provided van bus from terminal airport transfer at no cost for us. The room is clean and comfortable, the surrounding area is a wood so you may have plenty of green to watch in the room. The only negative point is the distance to city center. Book if you are arriving/departure Cologne, but be aware if you are staying for some days at city center that the distance is 30min by car.