Well, for me, getting the books sooner was worth it, because I want to use them starting now, not two months from now.
Amazon gave a "maybe" date, but from my experience with them before, some times they will get the books by that date, and some times not. Actually, in every other case where I have gotten a similar email saying that there is a delay and they might have the book by a certain date, my order ends up being cancelled a month or two later, anyway.
I do like supporting homeschool businesses that I like, when I can.