Rene's place is big, clean, has everything one would need, and is a five minute walk from Hauptbahnhof, Vienna's main train station. The four of us - co-workers and friends - used the apartment as our base for a three-day office retreat and never felt cramped, that's how big the bedrooms are. The kitchen is beautifully done and very well equipped.
Only some minor points to mention: the shower has no curtain, which results in wet floors every time someone takes a shower; the street in front of the building is quite busy in the morning and if you keep the window open you might be woken up early; and the front door feels a little shaky and not terribly solid, which prompted some of us to take their laptops with them when leaving the house. Each bedroom has its own key, which makes this perfect for a group of people.
Oh, and across the street is a wonderful restaurant, Das Lokal Im Hof.
So all in all, very happy with this stay.