I can confirm this happens. Basically, when Compiz (Desktop Effects) is on, the gnome-screenshot dialog box is still fading away when the screenshot is taken.
The resulting screenshot has a translucent gnome-screenshot dialog pane as a result.
When Compiz is on, Gnome screenshot should automatically have a default delay equal to the fade speed settings in Compiz.
I can confirm this happens. Basically, when Compiz (Desktop Effects) is on, the gnome-screenshot dialog box is still fading away when the screenshot is taken.
The resulting screenshot has a translucent gnome-screenshot dialog pane as a result.
When Compiz is on, Gnome screenshot should automatically have a default delay equal to the fade speed settings in Compiz.