Loved this, easy to pick-up, we drank cocktails in the bar and skipped relaxedly through a lot of the information then pottered off to view the most interesting bit. The Oyster bar is well worth a visit to while you're in Grand Central Terminal.
Really fun and easy. Took about 45 minutes to do the long tour by audio, but a little bit longer because you end up talking about the beauty of the place. It was simple to use. Great for a rainy day in New York