I am still not clear if there is a difference between the pre-order bonus in-game content and the "buy it the day of" or "buy it a week later" in-game bonus content. Pre-order has additional physical content (fold out tech tree) but is the in-game content all the same? Put simply: how many in-game bonus content packages are there?

As far as I can tell in terms of "buy it the day of" or "buy it a week later" there is the collectors' edition and the normal edition, the Collectors' edition has the extra components and tech tree while the normal edition probably wont.

If you pre-order you are almost guaranteed to get the Collectors edition (except if you ordered from Amazon Link ) which has all the extras.

Now the confusion is that if you pre-order from Stardock you can download the game where you get the extra in-game content of the collectors edition without the physical stuff. However, they will let you grab the CD later although I’m not 100% on the details of how.

OK, one more thing to add to the confusion... ) If I order through Wal-Mart.com will I get the pre-order items? It does not list anything about getting any bonus material what-so-ever. Can someone definitively answer this for me, please?

If you follow the Link I just posted (provided it works) Brad has confirmed that Wal-mart will have the Collectors edition in the US, while maybe not in Canada.

Would they be missing out on any in-game content for not having pre-ordered (but still getting collectors edition)?

This is a very good question because many times EB will have titles with the bonus content for weeks or months after.

Just look at Empire Earth II on EB you can still the bonus material if you order it now. I am not even sure how long it has been out at this point as I do not own it.

http://www.ebgames.com/ebx/product/243571.asp Empire Earth II Link with Bonus