Gaiman versus Whedon?

[chicken]

According to JoBlo.com, Neil Gaiman's "Mirrormask" is coming out on September 30, the same day as "Serenity". In my estimation this would not be good for either film since Whedon fans and Gaiman fans tend to overlap a lot. If people are forced to choose, that could drive down those crucial opening weekend receipts for both films.