This is what Gnome 3 looks like on dual monitors, the wallpaper is spanned across both screens on the wide desktop but the Gnome panels are stuck on one screen. This is one of the consequences of developing a desktop for touch devices that can not use dual screens, you only see these bugs on a desktop machine. Or a laptop with an external screen attached. Please fix this Gnome! This is mentioned here but this is an older posting. There is a newer posting here also that indicates there are still some issues with dual monitors on Gnome 3. I wanted the panels to stretch across both screens like you could with other more sane desktop environments but this does not work as of yet.
I had to create a custom wallpaper for this screenshot as I did not have any 2560*1600 resolution wallpapers. But I hope this will be fixed very soon or there will be some people that will get very annoyed with this desktop environment and move to MATE or Xfce. Surely with other window managers you can edit your /etc/X11/xorg.conf and put in the settings manually for dual monitors, but you should be able to do this at the desktop like Windows 7. Anyway, the ability to install Xmms in Fedora Core 15 lifts it above the likes of Ubuntu that does not have that excellent music player in their repositories anymore. And that is a dammed shame. The audacious player has a good range of codec support and can look just like Xmms. I really should purchase another flat panel monitor for my system to allow me to test dual monitors with Cinnamon and KDE 4.8.0.