I'm confused about all the talk about interior templates and formatting. On advice gained here, I took my Word doc (no headers, footer, page numbers), ran it through D2D to get a pdf, then ran the pdf through CreateSpace to make the books. I had read all the horrors of formatting and templates but never even ran into them.
That's because D2D did all that for you using a standard template they have. If you look in your PDF that they generated for you there are likely headers and page numbers. But many of us, including me, aren't huge fans of the look of the D2D PDF. Or want more control over our paperback.
For example, for each new chapter do you want it start on the right-hand page or just the next available page? Do you want your chapters to have different headers or is the same header throughout the entire book okay with you? What about if you have a chapter that ends with just one line on the final page? Okay, or do you want to tweak paragraph spacing to pull that line back onto the prior page? What about section breaks? Do you want two spaces (whereas maybe your e-book uses a symbol) or do you want a special symbol that isn't used in your ebook? What about font? I use a different font for my non-fiction versus my fiction and a different font size. What about book size? I've used two different book sizes for my books and I don't think either are D2D's default.
So, yes. You can go through D2D, they'll generate a PDF in thirty seconds, upload it to CS, and go. But...At least for me personally, I'd rather download the CS template and tweak it to get the look I want. YMMV. It takes me five or six hours for a print book. With CS, I could be done in five minutes.
And, in response to Amity Lassiter's comment about the physical proofs. I would definitely recommend always reviewing a physical proof. (I also read each physical print and inevitably catch another handful of errors or decide that I really didn't need this comma or that one.) For a couple of my books I had to completely change up the covers to get them to work in print. What looked like red on my screen came off as bright pink in print, for example. If you can't do that, physically print your cover page to see what the colors look like in print. It's not the same as on your computer screen. (Unfortunately, the thumbnail is then what works for print...)