It was extensively talked about in theserverside.com, see this link:
www.theserverside.com/.../thread.jsp
Anyway, for sure Sun’s pet Store example is one of the worst apps I’ve ever seen, too much complication for nothing valuable. It tries to give you an MVC mechanism and supposedly flexibility but in reality you only have more things to do when you want to add a simple action to system. The code is unbearable, as Martin Fowler says “The design is in the code” but take a look at the bloody code and you realize there’s no neat design beneath it too! It’s a classic example of “Over-designing”. The guys who wrote it should have been fired :o)
Anyway, I downloaded MS petstore and I really didn’t find it interesting (though I’m not a .Net guru), yet anther spaghetti code from MS