I've been to Penny's twice now, and both times enjoyed the experience. Penny's comes from the Tom's Diner family, so I expected Tom's Diner type food, but I was pleasantly surprised to see different kinds of food, and a much bigger menu then you normally see at a Tom's. There's also a definite Greek vibe to the place, from the baklava at the hostess desk, to the avolemono soup (one of the best I've had in Pittsburgh) and gyros. The portions are big, the food has that awesome diner style, the coffee is just right, and I haven't had anything I haven't liked yet. Also, make sure you try their rice pudding- mmm.
By the way- any restaurant that uses two grilled cheese sandwiches for a burger bun is always a winner in my book.