With a couple edits to xorg.conf you can get Compiz working pretty much out of the box without XGL enabled! SWEET and a first - the Gutsy Gibbon is looking good.

Make sure you are using the fglrx driver (See System > Administration > Screen and Graphics). Open /etc/X11/xorg.conf in your favourite editor and add the following to Section “Device” Under the Busid Option:

Option "backingstore" "true"
Option “EnablePageFlip” “true”
Option “SubPixelOrder” “none”
Option “AccelMethod” “XAA”
Option “RenderAccel” “true”
Option “AGPMode” “4″
Option “ColorTiling” “on”
Option “DynamicClocks” “on”
Option “mtrr” “on”
Option “VideoOverlay” “on”
Option “OpenGLOverlay” “off”

Check that under the Section “Extensions” that the Option “Composite” is enabled, i.e.:
Section "Extensions"
Option “Composite” “Enable”
EndSection

Finally enable Desktop Effects via System > Preferences > Appearance > Desktop Effects.