Insight
Adventurer
I used to play VtM and then bought VtR. I wound up converting some of the VtM crunch into VtR and then using the Camarilla as my backgrounds for the game.
They fixed a few of the VtM rules in VtR that I felt uncomfortable with. But I still liked the Sabbat/Camarilla backgrounds for the game.
I did not like some of the new vampire bloodlines in VtR, so they wound up disappearing and bringing back some of the original bloodlines.
Yeah, there's no reason you couldn't take the rule fixes from nWoD and use the background/fluff from oWoD. I'm not sure how much this applies to Mage and Werewolf, since the vast majority of my experience in oWoD was with Vampire and I haven't played enough nWoD to recognize any differences thereof.