When in a "normal" folder view, Enter on a selected folder or Double-Clicking it are equivalent actions.  Both do the same thing: navigate into the folder.

However, on the search results list, they are subtly different:

- Double-click exits the "search view" and navigates into the folder.  The navigation bar shows breadcrumbs leading the folder and the main view shows the contents of that folder.  One can go back to the search results by hitting the back button or Alt-Left, and up in the folder hierarchy with the breadcrums or Alt-Up.

- The Enter key, leads to showing the contents of the folder in the main view, but it does not exit the "search view".  The navigation bar still shows "Search for 'foo'".  Furthermore, the navigation keys seem to be in a broken state, both Alt-Left for Back, Alt-Up for moving up the tree do nothing.

Not only is this distinction confusing, it damages keyboard interaction: it is specially important for the navigation keys to function properly after pressing Enter, since it is to be expected that users that navigate into a folder with they keyboard will also do other actions with key combinations.

In fact I wonder if the current behavior is intended (I would consider this then a UX bug) or maybe it is a missimplementation of keyboard navigation for search (something equivalent to Double-Click was always intended).  In any case, a small glitch in an otherwise excellent piece of software with great design :-)