I stayed at the NH Atlanta for a night earlier this week. The location is fantastic- 3 minutes walk from Stadhuis Metro (line E to/from the Airport takes just 15 mins from here), under 15 mins from Centraal Station and is within walking distance to all the shops, nightlife and attractions of Rotterdam.
All the staff were brilliant- very friendly and nothing was too much trouble. The food was good (breakfast in particular was an amazing spread) and room service was efficient and good value.
My 4th floor room was spacious enough, with excellent amenities, tea/coffee, a decent mini bar and a comfortable bed. Only negative is that the rooms are a little tired and clinical in terms of the decor.
All in all a pleasant stay, and I'd certainly return next time im in Rotterdam. More