On some systems (like Fedora 15) the Compositor is turned OFF by default, and this quietly removes other XFCE options. This means that Joe New User won't see a number of XFCE capabilities. Instead, such options should be shaded gray to indicate they can't be currently selected, and some text displayed like "To enable varying the opacity, enable a compositor. You can do this using the window tweaks application." This should be done wherever compositor-dependent options are placed. This would be REALLY helpful for new users of XFCE. Similarly, there should be help text on the "Window manager tweaks" to explain what a compositor is, and why you would or would not enable it. A checkbox labelled "Enable display compositing" doesn't explain it. Thanks!
True. Fixed in 4cce36d.
Excellent! I'm yet another refugee from GNOME 3 (http://www.dwheeler.com/blog/2011/08/03/#gnome-3-shell-terrible-switching-to-xfce), and I appreciate what you XFCE developers have created. Thanks for all you've done!