As far as I'm concerned, fixing #36 only requires to change the folder name to something more appropriate (and doing a migration script if needed).
Allowing to set an "application name" is probably useful, if it can be implemented in most backends, although I think it would probably be less restrictive to be able to set a "comment" or "detail" on a specific password instead.
Jonathan you're right, issue #36 is not connected with setting "application name".
I can post a separate pull request for the folder name.
But I not agree that only folder name should be changed. I think we should use KWallet's folder functionality appropriately, each app in it's own folder and without "@ service" suffix.
About the "application name"
I'm not sure how other keyrings handle it but KWallet shows a prompt saying which application asks for the access. When you see the app name your know that it's you(or not) that caused it. It gives a little bit of certainty for the user, he knows whom he gives access.
Gnome also seems to show the application name on it's UI prompt.
Regarding backward compatibility - I'm inclined to say let's keep backward compatibility using option 2 or 3. I agree, option 3 sounds messy, so let's go with option 2. Even if we just have that for a short-lived interim release before breaking backward compatibility, it gives most users a much smoother transition.