Just returned from Berlin, we stayed 3 nights in NH Potsdamer Platz. First of all it has an excellent location, just 10 minutes walk from Potsdamer Platz, about 15 from Reichstag & Brandenburger Tor. U Bahn (metro) & train stations are also very close about 5 minutes walking. the room was abslutely great, clean & spacious. the staff in the reception were very helpful and were happy to assist in any kind of question regarding sight seeing in Berlin, transportation etc... Breakfast was very good.
I would recommend this hotel to everyone!