Myself, my wife and 5 year old son stayed at the Mandala Suites on Friedrichstrasse for 4 nights starting on 31st Jan 2016. We had an apartment with a king bed and separate living area.
First thing to say about this accommodation is that it is not a hotel (stating the obvious perhaps) so don't expect all the extra services such as concierge, room service etc.
This is not a criticism but I mention it so that expectations are met.

Second thing to say is the location:
This location in Berlin on Friedrichstrasse is fantastic for looking around central Berlin. You are 10-15 mins walk from the Brandenburg Gate and Reichstag. Friedrichstrasse itself and the street around have a huge range or shops, restaurants, interesting buildings (and if you are there over Christmas it is a short walk to the fantastic Gendarmenmarkt. And best of all the U-Bahn station of Stadtmitte is literally right outside the accommodation.
Using the U-Bahn was a great way to get around Berlin when we did not want to walk.

On the accommodation itself:
The apartments are part of a modern mix usage (retail, restaurants, offices) block with easy access from front and back.
They provide a nice reception area and on my arrival the staff were very helpful and sent the bags up to my room.
The apartment itself was enormous (in comparison to a normal hotel room). (I think I booked an Execute Apartment) and was plenty big enough for the three of us.
The apartment included a small kitchen (cook top, mircowave, fridge, pans, dishes etc) but no oven. It came is very useful when we did not want to eat out and just have breakfast or a light snack.
You can get breakfast in the apartments itself for an extra charge but we did not try this out as we made breakfast for ourselves.
The only thing lacking in the apartment (perhaps it was the layout of the type I booked) was a table and chairs for eating at. There was a small low table in front of the sofas but this was not a "kitchen table" that was easy to eat at. Not a major issue though.
Decor of the apartment was modern, clean although not inspiring in terms of interior design.

Other things to note:
We were in Berlin on 1st January and pretty much everything (shops, restaurants supermarkets) etc was closed - not surprisingly - a couple of cafes and Starbucks were open. Therefore having a self catering apartment was great as we could feed ourselves without having to worry about finding a restaurant.

Conclusion:
We really enjoyed our stay at Mandala suites. It was a big modern apartment with a great location for our needs.
I would stay here again if I need to be in central Berlin for a few nights.

Great large rooms, with excellent internet connections; helpful staff, a wonderful room for breakfast. In the midst of the city, you feel as if in another place- quiet, well appointed. A very beautiful space- perfectly organized, and very comfortable.