My copy of Halo 4 arrived today, so I played a couple hours of campaign. I have to say, I really loved the first level. After that, when things got a little more combat heavy/ they put you straight into one of those "Halo Warthog levels" but without the thing that makes it work (A FUCKING GUNNER/DRIVER), I started to play with the weapons, and I don't know that I like the changes that were made... The Carbine feels useless, except if you're really good at headshotting grunts, and then it's only useful for killing grunts. The needler is pretty awesome, but I'm sick of getting supercombined over and over (something past halo games were smart to generally avoid putting you through over and over) and grenades seem bizzarrely different depending on who throws them. I was between two grenades that had a good bit of distance on me and was killed. I set of a grenade at an elite's feet and barely dented his shields. Especially after Reach, where grenades were awesome (once they were brought down from beeing god like), it feels really lame. The Plasma fuse seems longer, as well.
The sniper rifle change seems especially unfortunate, making it more of a 2-3 shot kill at it's most efficient really ruins the fun.
Body shots seem to be pretty significantly different too. I don't remember the lowest tier grunts taking nearly that many rounds to the back as they do this time around more often than not.
I dunno, it's been a while since I play Halo, so maybe I'm just rusty, but I'm not loving the sandbox so far in campaign. Seems a little to multiplayer MLG focused, which gets away from what makes halo so fun: it's just fun!