I pre-order quite a lot of stuff (if only because it means I only have to order my classic Who DVDs once every three or four months, rather than continually checking back)
If you're going to have to wait anyway, you might as well take the hassle of checking back out of the equation, and there's always the "Pre-Order Price Guarantee" on Amazon, so you don't pay the often artificially inflated prices at release*, especially on books.
The only problem is when release dates get altered to just before payday(!)
*Yeah, OK, I really mean the actual RRP at release, rather than the artificially discounted prices you get months ahead, but you knew that anyway.