The soundtrack is good when I listen to it on it's own, it's just when I was playing the campaign it didn't stand out at all, more like background noise but if I listen to it outside of the game I quite like it. This is a new trilogy they wanted it to sound and look different than before, I understand the style change but they need better sound mixing and sync.
The campaign overall was forgettable to be honest, just like Reach. I don't remember much of either right now but I clearly remember 1,2,3 or even odst right now. well I still remember that horrible last encounter in Reach >.< Reach was just series of firefights and maps all were from multiplayer, it was really not good. 4 isn't a series of firefights and has more variety in environment
but enemy variety is far worse really, it's pretty bad. And vehicles, this game lacks vehicles very much, and vehicle based encounters. They needed more big levels like the mammoth one. I feel that with better hardware they can do much better and here their hands were tied really, still unfortunate.
The story telling is pretty poor too, Terminals shouldn't be about the main story but background of the areas you are in. Halo3 terminals were just a story in itself, not related to what was happening and gave more depth to the area. They should do something like audio logs in bioshock for the terminals and try making all these buildings and corridors more than just what they are, like the moment in Halo CE when you watch the log on Pvt. Jenkins helmet and their encounter with the Flood, Halo has had nothing remotely like that since then. Don't hide all the story in terminals, they are not for that. Really terrible decision this was and hurts the campaign quite a bit.
I'm really enjoying the multiplayer, it's something between CoD and Halo and not quite either, I like that so far. Spartan Ops was totally meh though. 343 should consider adding firefight back in in near future because this is not a replacement at all.