Published setting with moderate modifications, although, as more products come out and the setting evolves, 'my version' tends to become increasingly different.
For instance, playing in the Realms, back in the days when the only source of Realms material was Ed Greenwood's Dragon articles, it was a *far* different world than currently exists. My Scarred Lands setting had only the original 'eight victors' and none of the racial demigods added later, etc. As more and more 'stuff' gets strapped onto a setting, I find that it increasingly moves away from the stuff that initially attracted me to it. Vecna becoming some ubergod able to steal power from all of the other gods, for instance, was completely wrong for the Greyhawk setting, IMO, being more of a 'Realms-style' divine munchkin exercise.
Ironically, this makes shorter-lived settings, like Kara-Tur and Al-Qadim, some of my favorites. They still remain thematically consistent, and leave room for me to 'play.'