Thanks for putting this guy in his place, mouse_clicker - I was just about to do the same, when I saw your post. Saved me some time, you did.
Yes, the game is going to be completely different. Many things have been modified, lengthened, or added in compeltely. It also does not use the MGS2 engline, as mouse_clicker stated - it merely uses a near carbon copy graphical style, which looks much nicer than MGS2, what with higher-poly models, environments, and bump mapping on most things (although the animation seems to just as good as MGS2, if not better (amazingly), which could be Konami's work). Sound has also been completely redone, with quite a few conversations changed around to make things more clear and cinematic. Cutscenes are also much longer and action-packed as well.
It's Silikon Knights' game, not Konami's. Konami is merely overseeing the production so it's done to their satisfaction, nothing much more.