We stayed at the Hotel Fuerst Metternich for 6 nights, mid-October 2011. Be aware first, that the photos are very misleading.
Pros: We found the room spacious and the beds very comfortable. The room was clean and very quiet. The location is good: just a block from the U3 U-Bahn station, and it is walkable to the Museumquartier or to the Ringstrasse. There is free wif-fi available, although the signal is weak in the room; better coverage in the lobby.
Cons: The room was overly warm and stuffy [but we solved that by keeping the windows open]. There is no kettle for heating water for tea or coffee in the room, and guests are asked not to use such devices if they brought them [I assume the wiring is old and inadequate]. Although there is an elevator, you will need to climb steps [with luggage] to the first floor/reception, and then there are many "half floors", so you will need to lug luggage another flight. The people in reception were indifferent about providing assistance. The breakfast is overpriced at 13 euros -- go a couple of blocks on Mariahilferstrasse to the Cafe Ritter and enjoy better service, cheaper prices, and a more homey, Austrian atmosphere.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC