Bungie bow-out at the top of their game.
And making a welcome return from Halo: CE is the amazing level design. Many times you'll be in awe of there environment you're playing through and you'll really feel like you're just a small part of something that is epic in scale but never lost or without direction.
On a bum-note: I really wish Bungie would do something about the friendly A.I. driving skills. Jumping on the back of a Warthog manning a massive rocket launcher should be amazing fun but I found myself having to take over the driving myself, the A.I. would always get stuck.
This game does deserve its 9.5 review score. And buying it won't be a waste of money.