Oh wait, it's a different Halo, sure, but I know it won't be another KZ2 alright. They said recently, if I recall correctly, that on the screen they can have 40 A.I.s all around and more than 20 vehicles at the same. That's quite something! Like any typical Halo, I believe the vehicles will be an important part of Reach. With that said, it's probably only the graphics that will change, oh and maybe the customization on your character and stuff.
Halo 3: ODST was darker than previous Halo games, but it wasn't as successful as the other Halo games because it didn't have a multiplayer component of its own. Plus, the campaign mode was a hit or miss. The hub is really really boring, sadly, and the missions are not long enough. It was a nice little game though, but I believe it was hard to justify buying an "expansion" for 60$ with the same Halo 3 multiplayer experience.
Random game thought :
Why is Bionic Commando Rearmed 2 getting so much hate? We finally get a real game and they're not even satisfied... I'm starting to hate the gaming community so f****** much...