Does Nick enjoy the afternoon at the New York apartment? Why or why not?

It would be fair to say that Nick does not enjoy his time at Tom's apartment in New York. He doesn't explicitly say so, but from his description of what happens, it's a fair assumption that he doesn't much care for the occasion. For one thing, there's something rather tawdry about Tom's place; not surprising when you consider it's his bolt-hole for conducting clandestine trysts with Myrtle Wilson.
The little social gathering encapsulates the deep social gulf between Tom Buchanan and his mistress and her family. Myrtle is a new woman as soon as she puts on some glamorous clothes. She starts to behave like a duchess, showing off her rich lover to her sister and some friends, acting like she has it made. Drink only makes her worse; copious amounts of booze turn her into a female version of Tom, assuming his same air of social superiority.
Nick is caught in the middle of all this. He already knew that Tom wasn't a particularly pleasant guy, but when he casually almost breaks Myrtle's nose, it's still a shock to see just how brutal he can be.