It does look awesome and I was going to get it, but if you preorder MGS4 you get Metal Gear Saga Vol. 2. The first Metal Gear Saga DVD was all about the games history, it had some other things. It's really cool if you're a big MG fan (like me!). Anywho, while it's a nice package, I really want preorder stuff, so maybe I'll get both the trade back one of the game copies or something.
Oh, and also, if you have a PS3 and Preorder MGS4 you get the beta for MGO in April.