Apart from a few tuneups, this update is primarily about built-in support for referrers.
Say you have a product hierarchy like this:
We are then often tasked with listing or in other ways extracting products based on a selected category (or media, as could be the case in this example). In the simplest of forms, the output could look like this (although I hope no live site would ever look like this :P):
With DomainObjects this is now a very straight forward piece of code. All based on an article by Lars Floe Nielsen which I often refer back to.
Sitecore 6 package, sources, API documentation have all been posted to the Trac space.