Comment 2 for bug 1027792

Well, the predictability is also something that is not given. Some apps behave quite different than others.

Lets assume all of the apps have at least one instance running:

Firefox: Opens new window on current desktop.
Thunderbird: Gives focus to the app and brings me to the desktop it resides on or lets the icons just wiggle. But most of the times the icon just wiggles.
Terminal: New terminal on the current desktop
Empathy: Moves the contact list to the current desktop.
Eclipse: Gives error message, since it's already started. (Workspace in use or cannot be created, choose a different one.)
System Settings (Ubuntu): Switches to the desktop the instance is already running.

It might be a design decision for Unity, but it's not predictable for the user what the application lens is really doing.

I think the user would benefit much more from this behavior:

1) App is not running: App gets started on the current desktop and gets focus.
2) One or more instances of the app are running: If the app hast just one window, the user switches to the desktop the app is running on and the window of the app gets focus. If the app has multiple windows, the user switches to the desktop of the last used window and this window gets focus.