There's one thing I'm sad they missed out during the Wildfire exposition scene (though I suppose it's not inconceivable that it could crop up again later).
In the books, after Tywin orders the alchemists to begin mass-producing, they're surprised at their own level of success in meeting his demands for production volume - it's always been tricky to produce, but now their yields are well above expectations.
Tywin assumes the alchemist is lying or faking his figures, and certainly isn't mollified when the man can't even explain his own success. The alchemist does offer one possible explanation, which Tywin dismisses out of hand - it seems that wildfire was said to be easier to make before the dragons died. Could dragons have somehow come back into the world?
Including some variant of that scene would have been good in this episode - it would underscore the comment that "dragons are fire, and fire is power", and it hints at the true magical nature and potential of these beasts, that their mere existence, all the way off in Qarth, is affecting the very nature of the world, even in King's Landing.
