After many years, I finally went to Botin two weeks ago and had the "cochinillo". It was fantastic and the restaurant was everything it was billed to be.
That being said, I had a better time at "Posada de la Villa" in November. The food was equal, the menu was more varied, (minus the cochinillo), the bread was better, the house red is Marques de Riscal Gran Reserva and to this day my dining companion shows me the front door key we got at the end of the meal!
Give it a try.