My introduction to D&D involved the Wilderlands.
In the late 70s (A Farewell to Kings by Rush had just come out, so 77/78), I used to sneak down to my cousin's basement where he and his stoner friends played D&D on a ping pong table. I never played (I was 8 or 9), but I thought it was pretty neat.
About 10 years ago, he told me he ran CSIO/Wilderlands, using OD&D, with parts of Greyhawk and Blackmoor, and of course, the JG material. Back in the day, he said the local hobby shop had all/most of the JG stuff as it came out, and he picked up a bunch of it.
As a result, I picked up some JG stuff, and have read through it from time to time. It's kinda like the background radiation of D&D for me. I can't place my finger on anything that the JG stuff has had a direct influence on my way of playing the game, but I'm sure it's there somewhere.
It's interesting to note that the same hobby shop is still open, though I don't think they do games anymore, just model railroad and RC planes/cars/boats. It is the same hobby shop my Dad bought me my first gaming material: the Modlvay Basic set and a few weeks later, 1st ed Gamma World.