I have stayed at the B2 twice while traveling for work (April & May 2013), each time for one week.
The staff at the B2 are extremely friendly and helpful. They always greet me by name and remembered me when I came back for my second work trip (a month after the first one). During my first stay, I had issues with lost luggage and stolen items from my luggage, and the B2 staff helped me figure out how to file a police report and really went out of their way to make me feel especially comfortable at the hotel, even though my situation was not at all their fault.
The hotel rooms are quite spacious by European standards. The beds are comfortable and the bathrooms are luxurious, with heated tile floors and rain showers. One minor note: the two different rooms I've stayed in did not have bathtubs; I don't know if any rooms do, but if having a bathtub is crucial for you, you should inquire in advance.
The hotel, even when completely full, is extremely quiet. The entire building is only about 1 year old, and the place is pristine. I have not yet had an opportunity to enjoy the spa, but all of my colleagues who have visited the on-site spa & roof-top pool tell me that the spa is amazing and well worth the small fee.
There are a number of shops and restaurants within a 5-15 minute walk, but because my office is just next to the hotel, I have had less need for shops and restaurants so am not able to fully comment on the location of this hotel as a vacation spot.