If you go you MUST try the Mutton chop (actually a yearling lamb) It's their signature dish and it's the only NY steakhouse that has it. Dry aged Prime Strips, ribeyes and porterhouse steaks can be had in any of the NYC steakhouses
I ate a Keen's several years ago for my brother-in-law's 60th birthday and really liked it. Of course I thought the pipes were really cool and the place had a nice Nineteenth Century vibe but, more importantly, the food was very good. Based on that positive experience, my wife and I went back at the end of this June for my birthday. This time, I found the food disappointing. We ordered the porterhouse for two, rare, and it came almost rare. It was too much for the two of us to eat so we were able to find enough rare pieces. The taste was about average for a New York steak house. The creamed spinach was tasteless but the baked potato that we shared was fine. The waiter brought me a complimentary wedge of cheesecake with a candle in it for dessert, which was very nice. The cheesecake was good. So overall, based on two visits, I'd have to say mixed review but certainly not awful.
Sitting next to us were four Japanese business men, each with his own T-bone that looked quite large and tasty. The gentlemen looked very happy. On the other side was a young family from Australia, who asked us what to order. The restaurant attracts about fifty/fifty New Yorkers who love it and visitors to town who are attracted to its old NY charm. In fact, Keen's without attribution was featured in the Showtime series, Billions. Chuck and Connerty each have a mutton chop for dinner because that's what alpha males do!
I have eaten there three times, all in the 1990's, the last time with well known New York area collector the late Jimmy Booth, so my memories of three entirely pleasant meals are tinged with sadness. Jimmy was the only person I ever met with a truly photographic memory. He could scan any printed page, then look up at the ceiling, blink his eyes and then recite it word for word. And he loved pipes.