v1.5 has been submitted to the marketplace. If all goes well it should appear in the marketplace soon. This release has a lot of not so obvious changes but the two major features updated are the addition of search and integration of the Windows Phone sharing.
Search allows you to search 500px photos for keywords and returns an image collection that you can mark as a favorite or pin the search to your start screen just like any other image collection.
Sharing now supports whatever email or social networks are registered with your phone Facebook, Twitter, etc.
One minor change in the user experience category is that when viewing an image’s details, the image appears as the background.