Ubuntu – How to use “Initiate Window Picker for window group” in Compiz

I use Unity and Compiz on natty. I have Scale and Scale Addons enabled.

I set
CompizConfig Settings Manager > Scale > Bindings > Initiate Window Picker for window group to set my keyboard shortcut for "Initiate Window Picker for window group" to Super+grave (using grab key combo). If I open several gnome-terminal windows and hit Super+grave, nothing happens. Same for empathy, nautilus, gimp, and chromium. I've also tried binding to Super+a.

How does this feature work? What am I doing wrong?

I expect it to work like Application level Expose on a Mac where it lets you switch through all windows from a specific program (all Finder windows or all Chromium windows).

Static Application Switcher's "Next window (group)" feature works as expected.