have to agree with hitman, playing reach is just epic. its like Halo: Combat Evolved but on growth hormones mixed with steroids and speed and in high def. The elites are back since this takes place prior to the brutes taking over and man, the elites are some serious bad @$$ mofo's, they're quick, they're strong, and they're mean. Being able to fight along side other spartans is just kick ass. The friendly and enemy AI is pretty damn smart.
Some things that I really like about the new game:
Any changes you make to your character (armor, colors ,etc) are reflected in all in game vids and views.
Armor upgrades - jet pack, armor lockup (prevents you from taking damage), hologram (a holographic image of you runs around distracting enemies), bubble shield, etc. Gone are the pickups that you had in Halo 3 that I found severely annoying since I was constantly dropping them because I was used to using 'X' to reload.
Nightvision mode: although I was extremely let down by Halo ODST the nightvision mode from it has been ripped into Halo Reach. Instead of running around with a damn flashlight your spartan has nightvision.
weapons: the new weapons are just kick ass.
graphics: wow, drool, i think i read somewhere the polygon count in Halo 3 for the assault rifle was somewhere around 80 polygons and the new system on reach has over 300 polygons just in the assault rifle alone. The graphics are crisp, both gameplay wise and in game video wise.
-----------------------------------------------------------------
I honestly admit that I have been a Halo fan since playing Halo Combat Evolved, I didnt think Halo 2 was that great, Halo 3 I liked, Halo ODST I didnt, but damn, Halo Reach is by far one of the best games I think I've ever played. I havent taken time to play multiplayer yet but I cant wait to dive into it to earn points to customize my armor options.