There are a number of aspects of the model api that have been bugging me for some time.
For instance, Feed.getEntries() returns a List, however, Feed.getEntries().add(...) doesn't actually do anything. It makes more sense for Feed.getEntries() to return an Iterator given that it's primary purpose is iterating through the entries. Doing so also allows us to optimize the underlying Axiom code (which provides efficient element iterators). There are also methods such as setCategories(List) that accept a list that I'd like to remove mainly because I haven't yet come across a use case in which building up the list of items separately then setting them on the element makes any sense. These changes would simplify and optimize the api a bit more. If there are no objections, I can check in a fix today. - James
