One of my long-time characters is a vampire (playing out the weaknesses has always made it... well, not a NORMAL character, but I enjoy glass cannons.), and one of the runs someone ran for me involved some ED ties and the Ordo Maximus. At once point, he got to listen in on a conversation between someone he never identified but revealed out of game as an Immortal Elf and one of the exceptionally old Nosferatu high up in the Ordo. The Immortal Elf treated the Nosferatu (who may have been a 4th Age creature, himself) with disdain, not only because of his blood-sucking, megalomaniacal nature, but referred to him, and all Infected, as "False Immortals."
I always enjoyed this notion, that a dragon or IE would not consider the Infected's version of agelessness as a cheat, or a counterfeit.
As for the SR-ED ties, over-use in early editions aside, I've always enjoyed the crossovers, at least for world-building purposes. When you're building setting details for yourself, it's an incredibly rich resource. I can remember a run I did using Tainted Orichalcum from the ED Gamemaster Guide. Drove all the miners insane during the Hailey's Comet.
I also liked the idea "Ultimate-Level" NPCs. It's not that I like the Mary-Sue effect, but around 3rd ed, when it was saved for the likes of Lofyr and Hestaby: creatures so damned powerful, ancient, mysterious and wise that they are capable of whatever they need to do. Stats kind of... made them TOO tangible? I'm not sure how to say it. I suppose looking at the numbers is like finding the borders to an unexplored frontier. There's less to explore, or it at least feels that way to me.
Is Living Room Games still holding EarthDawn? Think they would mind SR doing the occasional (RARE) crossover?