Left me with mixed feelings. At the time of visiting, Prague was the only other big central European city I had been to, and since I enjoyed it so much I couldn't help but compare. A lot of people seemed to tell me to go to Budapest when I told them how much I liked Prague. But Budapest has much more of a disjointed aesthetic and is architecturally very different, even on the less disjointed Buda side with its Castle Quarter.
That said, it has its moments. The Széchenyi Baths (old TWHS) was genuinely a really enjoyable experience despite the crowds and not an insignificant amount of people seeming to dislike them. The Jewish Quarter (another old TWHS) with its synagogues, gives you an authentic glimpse into the city's rich Jewish heritage. The Danube evening cruise gives you some great views of the illuminated Parliament building and other landmarks on the banks of the river, and for me felt like the best way to appreciate the OUV.
The underground cave system (TWHS) and the underground Hospital in the Rock museum are really cool and worth seeking out. Other than this, some of the outskirts like the Gellért Hill area (pictured) gives you a good panorama, and the City Park area also has its charms. But other major attractions fell flat, e.g. the House of Terror museum is rubbish, the Parliament tour feels overhyped, and supposedly iconic spots like the Central Market and even Andrássy Avenue (part of this WHS) are quite underwhelming.