Here's my take on the hotel - we had the same suite that
youhavebeenupgraded video'd (or actually the mirror of it, there are two of these on each side of the über-über suite)
Location - excellent central location, right opposite the Opera. It's not on the river, so if you want river views, go elsewhere.
Architecture - a landmark building, lovingly restored to its former glory (as opposed to the Dorothea mentioned above, where basically they ripped out everything behind the facade and built a new hotel behind)
Room - this was a redemption. It cost at first 58k/night, revisiting the booking later it was 40k, so rebooked. Applied SNA, received a "Fantastic Suite". It was jaw dropping. One of the BEST rooms I ever had, with face on view on the holiday lit Opera and the main Andrássy boulevard. Good sound isolation, no noise from the boulevard. I keep saying "room", because technically I think it would be a huge room, with no separate sleeping and living areas/rooms. The bathroom was just "wow".
The cash price would've been ca. 350€ for the basic room, ca. 900€ for this suite, so 40k + SNA is a very good value proposition.
F&B - the site of the Dreschler café of yesteryear is the restaurant-cum-bar. Breakfast is table service only, no buffet. We also had lunch there, VERY good.
Personnel - Very young, attentive and enthusiastic.
Spa - didn't check it out
Now some of the not-so-positive things - must be nitpicking to find some
Entrance is from the side street, first time visitors might struggle to find it. From the boulevard there's only the restaurant terrace, which is closed during the winter season
Reception is a semi-hidden hole-in-the wall.
The view from the non-Opera-facing rooms are nothing spectacular, on buildings on the other side of the narrow side streets.
Would I return? Absolutely. Would it be my first choice? The jury is out, the Matild's location is arguably at least as good and their suite is an actual suite with free minibar use (!) So probably a strong second choice, depending also on price (€ or points) at the moment.
PS - the colloquial name of the building "Ballet School" comes from the fact that there used to be a ballet school in the building between 1936-2002