Except for some bizarre restrictions on functionality. You can drag and drop books onto the Kindle like a thumb drive (awesome!), but there isn't support for folders (not awesome!). If you want to organise huge quantities of books into collections which is, after all, the point of the Kindle, you have to do it manually on the device. Or you use Calibre, but I feel like that's a negative point because most consumers won't know about it.
Is it so hard to view as a directory structure rather than listing all the books recursively?
That and they seem to have removed the 3G for web browsing, so now owning a cellular Kindle is pretty much useless unless you're really desperate to get a book abroad.