Sorry to say I don't have any experience other than day-dreaming of the day I can install one at my house.
Might want to check with your local utility to see if any natural gas lines are near your property. If you were to roll it into a bigger project, such as converting your heat from oil to NG, you might get some sort of utility rebate or sharing of the gas line construction cost. (total speculation here)
The generators can also run of LP gas, so you could run it off a large(ish) refillable tank instead. If you look at the specs of the generators it will say how many gallons per hour it consumes at 50% load. For the 9kW model its 0.87 gallons/hour. Which means a 100lb tank would last a little over 1 day of continuous use. A 420lb "100 gallon" tank would last about 4.5 days at half load. Something else to consider.