Jeff; Sorry for the late reply but the holiday intervened. While I am not a greenkeeper, I have been a chairman for almost 20 years and work with the supers throughout Chicagoland. Accordingly, my opinions are those of an educated amateur. At Briarwood, we installed XGD on almost 90 year old push up greens 3 years ago. The greens were a mix of Washington bent, penn cross and , predominantly, poa. Root system was extremely shallow although we had engaged in aggressive topdressing for several years. As i understand it, many of the old push up greens, having been built before the installation of automatic irrigation, were built to hold water. XGD acts as a "release'; when the soil profile is saturated XGD causes the water to flush rapidly out of the system, almost like flushing a toilet. We have had rains of several inches and been able to cut greens the next morning. Installation took about 3 days for the entire course. Greens were playable the day after installation.
We did other things to improve drainage including several years of drill and fill along with regular aeration and verticutting. Nonetheless, after the horrible summer of 2010, our club voted to gas our greens and surrounds and plant an A1/A4 mixture. The project commenced in August of 2011 and the greens opened Memorial Day weekend of 2012. It has been a great success. The surface is very true, the greens drain beautifully. The new surrounds have created more ground game options as we cut them short and maintain them to be quite firm. We will see if we can keep them for a long time. So far they are everything we could have envisioned.