We stayed for a single night for a very reasonable price (82€ for a double).
The room was nice and clean, with a nice bathroom with shower and 6 towels and tv (free and pay-tv) and the whole building has been renovated recently i presume. Breakfast was included and the real big deal is its central position. I go to Munich almost every year and always slept in non-central hotels for a little less money than this. Definetly a great discovery.
The only two negative aspects were the lack of a refrigerator inside the room and the lack of a garage, so you are forced to park in the street or in the underground parking near the hotel (in each case you have to pay something like 20€/24h). Not a big drawback anyway, since this zone is very safe and Munich is one of the safest big cities in the world.
The hotel is located 15 minutes from Marienplatz by foot and 2 minutes from the near underground station.

Important: the check-in is done in the near Herzog-Wilhelm Hotel's reception.

At first I was not sure, you had to check in at a hotel around the corner, no biggie. This place was perfect for us. We had our extended family meeting in Munich for the Christmas markets. Hotel was perfect. Location: close to markets and U Bahn stop (you can take a train from the airport to within about two blocks of this hotel with one easy transfer). Breakfast was one of the better ones I had in several years of traveling in the EU. Price was very fair. We will stay there next year again.

We arrived at this hotel around 10 pm. The only problem is that you have to check in around the corner at another hotel. The man working the front desk was very nice, and walked us to the McDonald's a few blocks away on his way home that night. We were very lucky to have Peter working that night, otherwise we would have had trouble! The room was nice and spacious (we are a family of 5), and it was located just a few blocks away from the Marienplatz. It is a great hotel!

Other than the hot July weather (and no AC) the room was great and worked well for our family of four. Few hotels in Munich are large enough to accept more than three without two rooms, so it worked out economically for us. The location is about 500m from the Marionplatz S-Bahn station so travel was also easy. One night the restaurant below had crowd of laughing/drinking/smoking patrions which was only an issue because we needed the windows open to stay cool. Don't worry about the key situation... just follow the signs on the doors and its no problem. Room quality was good with a tiny show in the bathroom. Great morning breakfasts in a cheery setting.