The simplified / elementary Nautilus idea firstly begun with the 100 paper cuts for Ubuntu Karmic and it stated that the menu and columns are too big and take away space for the really important stuff. Unfortunately, a fix was never released. Here is where Nautilus Elementary comes in: a Nautilus patched for simplicity.
The Lucid Lynx version comes with configurable toolbar (either vertical or horizontal), a new widget, nice looking breadcrumbs and you can now configure Nautilus Elementary from within Nautilus. Of course, the old Nautilus Elementary features are still available in this version.