Folder structures sucks major balls, simply because there is only one entry point/one view, and it's so damn rigid. (ok, you can create more views if you use links, but that isn't exactly something you'd want to maintain)
Anything that can remove the importance of the structures when finding data (i.e. by providing alternative views) is a step forward.
I just hope that Zeitgeist isn't going to be the only alternative organization. Advanced "by date" is definitely an important step, but there's so much more.