From Facebook Developers Wiki

The new 'visible' statement are not anymore 'if' statement, so far it is impossible to do: <fb:visible-to-added-app-users> <fb:else><a...>Try this app!</a> </fb:else> </fb:visible-to-added-app-users>

That will always be impossible. That's the idea.

Request for above. There are ways to make this work and still accomplish what FB was trying to do.

[edit] This feature does not work

I can't get this to work. The content between the tags is visible even if the user has not added the app.

Can someone at Facebook respond and confirm if this works?