|Notify-OSD as seen in Unity|
So first off, open up a terminal You can do this by accessing the applications menu from XFCE, or in Unity by opening the dash and typing in “terminal”. Once the terminal is open, paste the following line into the terminal and press enter.
gksu gedit /usr/share/dbus-1/services/org.xfce.xfce4-notifyd.Notifications.service
After pressing enter, you should receive a prompt for your password because this is modifying high level parts of your system. Just enter your password and continue. A new gedit (text editor) window should open with that config file.
All you have to do now is replace one line of text in that file. In that file, just replace following line:
Exec=/usr/lib/xfce4/notifyd/xfce4-notifyd with Exec=/usr/lib/notify-osd/notify-osd
After that, save the file and log out. Log back in, and you should see Unity's notification system back. Note that after doing this, you will also get GNOME's notification system in XFCE.
If you do change your mind and want XFCE's notification system back, just edit that file again and paste the first line back to where the second line is located.
Hope this has helped you all, because this has helped me. If you have questions, let me know.