On my system with the latest org on Fedora, export-as-odt-and-open was not opening in an external problem for me, despite changing org-file-apps appropriately. In the code I found a 'system parameter that was breaking it, but I'm not sure why it was working for other people. You can see the details and my solution on SO, and anyone with an explanation would be welcome.
http://stackoverflow.com/questions/24434854/emacs-org-odt-export-as-odf-and-open-odt-outside-emacs
