It is not easy to summarize our stay at the Grand, because there were many great things, but also several drawbacks that made it far from perfect.
First the great things:
1) The room itself (640, one of the basic "superior" rooms) was really beautiful, cozy and big enough to feel comfortable at any time of the day (except for the temperature, as I will explain), with a comfy bed and very elegant bathroom (marble everywhere, golden tubs, double basin, good toiletries and plenty of space), And everything spotlessly clean.
2) Impressive common areas, with that old-fashioned XIXth century elegance I truly appreciate in these kind of luxury hotels.
3) Free wi-fi internet throughout the premises.
4) High level of service, including an efficient concierge, room service and housekeeping.
Now the drawbacks:
1) Too hot: perhaps it sounds pretty incredible (hot? in Vienna? in December?), but the entire hotel, and specially the room, was extremely and uncomfortably hot. There was no chance to lower the room's temperaure at will (in fact, it seemed the heating system was centrally controled); we tried just switching off the heating and opening the window for the whole day (and night) but, even so, it was too hot..
2) Noise: not from the street or other rooms, but from the hotel systems. You could hear an almost continous buzzing that could be ignored for a while, but that, added up to the hot, made impossible for us to have a decent sleep.
3) Bizarre credit card handling: we had to pay our room in advance and give a credit card number and authorization not only for that full charge, but also to let the hotel block an amount of 100 € per night of stay. Up to this point, a quite usual practice, considering it was New Year's Eve in Vienna. But, in addition, the day after our prepayment they blocked an equal amount (that is to say, several thousand euros) for whatever reason I still cannot understand (when I answered about it, the hotel told me there were no further blockings, but my bank was not of the same opinion). As a result, I had to negociate a higher credit limit with my bank before the beginning of the journey. At checking out, everything seemed OK again (the unexplained blocking had disappeared), but unpleasant surprises were not over at all. A couple of days after our return, we received a letter from the hotel, claiming that we had consumed a couple of things from the minibar (what we had not) and charging an extra amount again to our poor and exhausted credit card. We wrote back, rejecting that charge, and they answered saying the whole thing was a mistake, credited our card and apologized. At the end, everything was in order, and they proved to be good and swift dealing with their mistakes, but it is obvious (at least, in my humble opinion) a hotel of this level should not make (and cannot afford) these kind of mishandles with clients' credit cards.
All in all, a good experience, but not excellent.