Sky City isn't too bad, food-wise. It's something to munch on while looking at the view. However the price tag makes it a pricey tourist trap. I don't remember much about the prime rib dinner I had. It was acceptable but nothing memorable, apparently. It's just a so-so experience overall.
The one fun thing is customer interaction via the spinning dining room. The last time I went there, someone was celebrating a birthday and sent round a card and pen for everyone to write on.