I gained a much greater appreciation for Warhol's work once I was able to actually see his work in person. i.e. seeing the actual Brillo Box project has much more impact then seeing a picture in some book.
At the exhibit of his I saw in Edinburgh they also had examples of the work he did as a commercial artist for magazine advertising in the early 60s. He was a real life Mad Men. Also, saw for teh first time examples of the work he had done specifically for children also very cool...