My situation is this:
- I install Ubuntu, and then install xfce4. When I start a Xfce Session, every auto-startup application in Ubuntu auto-startup in xfce4 as well. But in the next Xfce Session, some application, such as Cairo-dock, start 2 instances, instead of one. Then everytime I start Xfce4 Session, I have two cairo-dock.

- Then I figure that it's because Xfce somehow save my session everytime I logout, and then when I login, it restore my session, and also call startup application. That's weird, because I have unchecked the "Automatically save session when logout", and also unchecked "Save session for future logins" in Log out windows. 

- There is a way to get rid of it, yet not very comfortabe. That's I have to check in the "Display choose on login", and everytime I start Xfce session, I have to New Session, instead of the Default one.

If I use Xfce only, I can still get rid of it by delete the old startup application, and create new one. But the problem is, if I do that, these startup application won't automatically startup in GNOME or KDE anymore.

So I want the Xfce session have more details configuration, such as allow people to create new session everytime. And more details in saving session on logout. And more synchronization with other desktop environment. I have use both KDE and GNOME and have no conflict like this.