RE: A really good slice of pie...
I agree that most NY diners are eminently boring, with all the ethnic fare we have here, why bother? Diners are usually the very last choice for me, and if a friend insists, I am grumpy and gloomy.
But, what about those huge cake/pie "exhibits", those revolving dessert displays? Is that where you saw your pie?
Some in-house baked are really worth it. For example, I go often to the "gourmet" takeout (forget the name) on 5th Ave bet. 19 & 20, and have noticed that the food is above average. Yesterday I read in their catering brochure that their breads are homemade, that in fact the originalk owner was a bread maker. They do have other pastries, so maybe I'll check out the pie.