Hi,
I have an xA and a SGII, and it is very helpful. It took a few tankfuls to calibrate it, but that is the case for any car. I mapped one of the X-Gauge readings (average MPG) so that I can have it on the main screen along with the instant MPG. I also use the throttle position, and the coolant temp; which helps a lot since the xA doesn't have a temp gauge.
You'll be glad you got it! Check out
my thread on aero mods for the xA. The grill block and fog light lens helped a lot, as did the zigzag tape at the top of the windshield.