Location, location, location! I loved staying here. The building is from the late 19th century and the Pension takes up the whole mezzanine level. My room was really cozy with tall ceilings and an updated, very modern bathroom. I arrived to a plate of fruit, some chocolates, a hand-written note, and a kettle for tea. Charming.
The room has a radiator and it had what I believe was an a/c unit on the room as well. The bed was really comfortable. I did ask for an extra duvet since they don't do flat sheets in europe and I tend to get cold when I sleep.
The bathroom has a shower with a real door so water wasn't going all over the bathroom! I will say that the shower was about 3'x3' but tall. I had no issues but someone who is more corpulent might find it a bit tight. I would say that's a tiny consideration and would not prevent me from recommending the Pension to friends.
The hotel has breakfast available each morning. I highly recommend paying for the breakfast when you book the room. I paid an extra $10/night. Had I waited until I was at the hotel to pay for breakfast, it would have been €16. Great breakfast. Eggs, bacon, sausage, fruit, cereal, toast, pastries...
My favorite thing about the hotel is that they give you real keys. You walk back to the hotel at the end of the day and unlock the door to a real Viennese house like a real Viennese resident. If I'm ever fortunate enough to be back in Vienna, I will definitely stay there again!