I neve bought a single Eberron product, nor a single Realms product, why? Because I hated the fluff in both of those settings. Realms is great to read a book about, but to actually play or run it is horrible from where I'm sitting. Eberron had no connetion with me at all.
I liked Greyhawk, but thought making it a "default" setting in .x was a bad move, it made it seem like it was the "basic" version of the game and one would go and play something else for more advanced play.
I won't be buying a FR or Eberron 4e product either for a half a dozen feats, some spells, and a few classes, unless they are totally devoid of any fluff. And then what's the point of putting the setting name on them in the first place?