After the opening, people were ready for a huge influx of visitors. However, few people expected such a rush: in the first twelve months alone, the 37-meter-high observation deck attracted about 4.5 million visitors, although the projected figure was 1.7 million. This is considerably more than at Neuschwanstein Castle and about the same number as at the Sistine Chapel in Rome over the same period. The Hafencity concert hall was reported on by media all over the world, with more than 50,000 articles published in Germany alone.
The stage in the main hall of the Philharmonic is located in the middle of the hall and after the opening a problem with audibility was discovered. The audience behind the stage could not hear the vocal performers well. However, this did not become a mass problem, was observed only a few times and depended on the particular performer.
In addition to the main purpose and three concert halls, the Philharmonic houses a hotel, apartments, and the Plaza observation deck. I couldn't find any information on the internet about whether the concerts are heard by the building's residents, apparently they are not.
All 45 apartments here are top of the line. From the 22nd to 26th floors, 4-bedroom apartments of 177-220 square meters were sold, and some are still being sold, for 6 million euros. Utility bills for such apartments are more than 3-4 thousand euros per month.
Entrance to the observation deck is paid, but inexpensive. It is better to book tickets on the official website (https://www.elbphilharmonie.de/en/plaza), as there may not be slots available on site for the next hour or two.
Getting there: The nearest subway is Baumwall (Elbphilharmonie). There is a parking lot at the Philharmonie itself, but it is the most expensive parking lot in Hamburg (https://www.apcoa.de/parken/hamburg/elbphilharmonie/).