I don't see much of a need for a GM screen...heck they sort of send one with the books. it's a bookmark. the system is fairly elegant and streamlined. There are two pages in the back of the book that pretty much are a GM screen, as it has I think, every single table in the entire game.
really i concur that just some web supplements are all that's needed with this particular system. I mean what's left to say about vampires that's not been said or isn't in the books themselves? what more rules do you need for them? And the magic system is so brilliantly open ended that idea is that there really aren't any "spells" mechanics wise, as everything is personal to the caster, so any spells in the book are just applications of the rules for you to build off of, and really...why pay for that? you get more dynamic help here, and it's free.
the only thing i can think of is as new monsters appear, or someone does something in the books that the rules don't cover (or can be covered but only after a really awkward and byzantine application).
A Never Never guide would be good too, especially with a "map" (which isn't so much about spatial relationships, as relative visual comparisons of the courts, and other known demesnes). bundle with it an abstract of the Accords.
