A good rule of thumb is, if you see a pre-order at Amazon for a really great price, jump on it. Amazon doesn't charge your card until the item is shipped so you can always cancel before that time should you change your mind.
Yep! With Amazon, it's a far far better idea to pre-order and later cancel (if you feel you have to) than to play the "wait and see" game. When it comes to CATALOG releases, Amazon pricing usually goes like this:
1) The day the title first available for pre-order is frequently the day it is the cheapest between first pre-order date and release date.
2) At some point between first pre-order and release date, the price will go up (sometimes by a LOT).
3) On release date, the price will almost always be higher than the first pre-order price. Sometimes the release date price will be a little lower than the highest price during the pre-order period, but the release date price will rarely be less than the first pre-order price.
4) After the title has been available for awhile, the price will likely drop below the release date price and, sometimes, even drop below the first pre-order date price.
Amazon's pricing game is very different for NEW releases. For CATALOG titles, the above is pretty much how it goes. Sure, there are exceptions, but not many.