It's a four-star hotel which doesn't really deserve all of its stars. We arrived there after a stay in a three-star hotel in Budapest, and each day, we remembered that Budapest hotel wistfully.
We chose what they call superior rooms which means our room had a balcony, a view of the lake Balaton, and an air-conditioner. Since the temperature was around 40 C, the a/c was much appreciated. People across the hall from us who didn't have it kept windows and doors open to get at least some air. Some people brought their own electric fans to survive the heat.
The rooms are large, and there their four-star quality ends. The beds were extremely uncomfortable. When I sat in bed trying to read the headboard came right up to the middle of my neck, and it was excruciating. The pillows were thin and uncomfortable, too. The bedframes were clearly designed to keep people out of bed and as far away from it as possible since I stubbed my toes more times than I care to count. The lampshades were dirty. The bathroom was cleanish, and that's the best that can be said it.
The food in the restaurants was good, and the menu for buffet breakfast and dinner varied pleasantly. However, make sure you know your German when you order lunch from a menu or drinks for the buffet dinner. No other language (unless it's Hungarian) will get you anywhere.
The hotel has a spa they call a beauty farm, and they offer very nice massages and baths. Although beware again that if you don't speak Hungarian or German you won't get very far there. The receptionists speak English, nobody else apparently does.
The hotel also has a thermal water swimming pool "with surprises," i.e. a variety of massage showers. The showers are great.
Most importantly, it's really a hotel for families with chidren. It's overrun by kids of all ages. And if you're not prepared to listen to wild screams all day long (we weren't), this is not a hotel for you. Kids start running around and shrieking their heads off as early as 7 a.m., and no matter how hard their parents try to keep them in check, it doesn't help. And I won't describe what they did with the showers in the pool, it defies imagination. The beach there is nice, but not many people swim in the lake itself, so the pools were really overcrowded.
In short, it's a family getaway, and unless you have a few kids you are unlikely to enjoy Club Tihany much.