I spent a week in this hotel and quite liked it.
It is not the most pretty of locations - the view is the street, then carpark, taxi rank, hot dog stands and side of HauptBahnHof - beyond which is the Cathedral. I was there for work so not that bothered myself.
I am Platinum, so was pleased with the upgrade to a suite, which was basic decoration but large enough and had a kitchen.
The hotel seemed to cater for mostly foreign touring coach parties on the whole - but was fine for me. I didnt use the restaurant at all.
For breakfast - there is an expansive mall under the station - with good snack and coffee bars.
For dinner - quite rightly, the centre of city is not far away, and due to proximity to railway lines - neither are Bonn or Dusseldorf - both worth a visit in the evening for a meal.
All in all, stay here if you are an avid SPG member, but not if you are used to life's luxuries.