I don't think anything of Importance is being let go...just from trailers I had flash backs to certain logbook entries in the previous 3 games. The ascended species and planet this time around was specifically mentioned in Metroid prime 2 for example.
Been a huge fan of the Prime series. Can't wait for this to hit the shelves! I don't even care if it's subpar...after the wiimote experience with the Prime 3 I'm ready to hit the next gen with a controller!
