We have it in ours - it was an OEM item but brand new when we ordered it (early 2015 model) We actually added it after the original order but before manufacturing was finished.
I think it makes the space much more usable, as it allows you to pull things out without having to crawl into the space. You do lose some room however, as it sits about 6 inches above the floor, but its worth it IMHO.
The dealer also said they could've ordered and installed it after delivery.
2015 Georgetown 351DS
Chris, Garren (humans)
Edgar & Carlos (felines)
RIP Sophie, the sweetest cat ever.