This hotel might be excellent if not for two issues.

The bed was really bad. Inclined so you slid aside while sleeping. Sleeping so, nights were not refreshing.

The safe box in the room was tiny, and they don't have any safe deposit facilities at reception. Had to carry my notebook on me at all times.

Not needing ultru-lux, we were very satisfied with this hotel, which we good on a good internet special. We were in the next-door hotel, so the downside was having to cart luggage up one lift, walk across the interconnection and then up another lift. Nevertheless, quite happy with the room and position. Location gets extra points... a few metres from the underground was an advantage, but plenty within walking distance too.
Did not eat in as there were plenty of options within walking distance. Could use a reburbishment in bathrooms.

Attending a show at the hungexpo, I had to find a hotel located between the airport and the expo. The Mercure Korona hotel is specially well located (25 mn from both destinations) and offers the opportunity to discover Budapest either by feet or taking the subway close to the hotel. Monuments, museum and shops are easy to reach in less than 5 minutes.
As far as services are concerned, reception staff is excellent and very helpfull. The restaurant offers as well classic as Hungarian traditional food. Swimming pool is also available.
A place to go!