Okay, here's the deal. You'd find other hotels in Vienna but Room55 is the perfect budget hotel with the luxuries of a big one. First off, its only a short hop on a bus from the State Opera at Karlsplatz or from the U station at Pilgramgasse (and with your transport pass, which I highly recommend you take, it's not problem at all). The check-in process is automated - you get key codes to the entrance and your room a couple days in advance. The rooms are some of the nicest you'll come across. The breakfast room is open all day and is in perfect condition always (discretion is the key for the staff). And in case you're going to be in Vienna a little after your checkout, the luggage storage is a welcome treat (I had my bags stored all day and returned after about 10 hours to an open breakfast room to relax and be on my way). Highly recommended!
Nice hotel close to subway
Overall it's a very pleasant place. No staff here, you get a code to let you in the hotel and room.
Just be aware that the hotel is on the ground floor. so can be a little noisy. but the street at night is quiet.
Also the hallway is not carpeted so very noisy when some guests comes in and out late during the night with their luggage....
Thanke you Karl