For me, it feels like Halo 2, just better, which is good actually.
I like the new equipment stuff, especially the bubble shield, not only does it look good, but it has very tactical uses. I saw this guy drop off the bubble shield and wait inside it with a shotgun, as soon as somebody steps in he drops them.
I also like the man canon, and the 3rd person view while carrying large weapons. I don’t like that weapon pickup and reload is not X any more, I keep doing that by mistake, similarly I don’t like that Y is not what you use for vehicle/turret entry (both are the right bumper now). That will take some time to get used to.
The graphics are much crisper than Halo 2, but still not what I expected, I expected it to look better than this, especially after the nice trailers they had released. Only the water looks good, but other textures seem low res to me, not what I expect from a next gen console. The under water sounds are just perfect and I love that.