Yeah, my books have been taking forever to be billed, but since they're downloading right away I'm not terribly concerned. I also bought the Hunger Games this week and it showed up on my nook right away, so like you I'm not thinking too hard about it.
The only annoying thing about their billing troubles is that the electronic gift card my dad gave me for Christmas took days to show up.
They can take their sweet time taking my money, though, as long as they give me the book first.