I went with 2 girlfriends and we absolutely loved our weekend break in Vienna.
Nikola was great at replying to any questions or requests and arranged his friend to taxi us to and from the airport for the standard fee - a very courteous guy who drives like Ayrton Senna !
The apartment feels very homely, cosy and easy to relax in plus being in the 1st District makes it an ideal location. You're 3 floors up (steps) and for me this was great as I'm a really light sleeper - even with the windows open, there was no noise.
One of us slept on the massage bed - very comfortable, as are the main beds.
Vienna is great - I've been to many cities on breaks but its definitely a favourite. Be prepared, there's so much to do and see, much more than we thought.
The hop on hop off bus is great to get an overview and the green line trip up into the hills was lovely too.
The opera house has a live feed screen outside for showings up until June - great atmosphere !
The whole city has a nice feel - very friendly and helpful.
I really recommend both Nikola's apartment and Vienna.