We were recommended this hotel / restaurant by someone who works for British Airways. Although we were staying elsewhere (the rather mediocre Boscolo), we came here for dinner on our last night. The food, ambience and - above all - service was impeccable.
The location was fabulous (right opposite the castle, on the bank of the Danube). The staff went to extraordinary lengths to make us feel at home, including offering us a selection of hors d'oeuvres (as we couldn't make up our minds which to choose - they all sounded fantastic), recommending a very good (and reasonably-priced) bottle of wine, and giving us for free a second dessert (when we couldn't choose between two chocolate choices! - by the way both of them were absolutely delicious).
The meal was not cheap (€193 between three of us), but that was for three courses and a very nice bottle of wine and includes the 10% tip. Considering the other meals we had in Budapest were so awful (including off food which made two of us sick at the Boscolo New York restaurant - stay far away from there!!!), and the fact it was my last night in Budapest, it was definitely worth it.
I regret not staying in the hotel. The lobby of the hotel is magnificent, both in terms of architectural style and in terms of decor (the Boscolo lacks the latter).
I'd really recommend you go there. Look out for the very tall tanned waiter. He's great!
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC