Downloading the digital version does not mean you will get to play at midnight. The digital version will allow you to play at midnight pdt. If you live on the east coast, it's 3am. I'm not sure how it works for other countries besides US. Look at the description at the store. However if you preordered a hard copy and your retail store is doing a midnight release, you will be able to play after you get home and download it.
"you may download the game before then(September 9th), but it will not be playable until 12:01 am pdt/ 3:01 am edt on the release date." -under digital description
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Good thing I live in california then.