Speaking with game experience with Halo 4 here: Halo 4 is definitely not like Reach, but it has aspects from Reach. If I had to give you the most concise way to put Halo 4 from my 2 hours of playing it at RTX, I would say
Halo 3 Game Pace + Halo 2 BR + Halo Reach DMR + Halo 3 + Perks = Halo 4
Overall, the game is balanced and a ball to play. It definitely has the potential to be THAT GAME
Killstreaks are only in Infinity Slayer, and to be flat out straight, it just feels great to get an ordnance drop. I know you will not believe me, but you'll wait until you play it.
TBH, I was heavily surprised when I played Halo 4 for the first time. The game just feels "great". It is what Reach SHOULD HAVE BEEN. It keeps that original Halo feel, and adds an interesting twist.
[Edited on 07.25.2012 12:58 AM PDT]