I don't know what it is, maybe I just set my expectations too high for games these days. I know Reach got a lot of hate, but I INSTANTLY loved that game and thought it felt incredibly fun and satisfying to play. I guess I feel kind of cheated because of the stellar reviews this game got.
I've seen others complain about it, but honestly the physics are one of the main things bothering me, especially in multiplayer. The game feels very loose and "slippery" to me. I've also gotta say that the killcams, ordnance drops, and loadouts are getting to me, even though I didn't think they would. The pacing just feels too fast for a Halo game; too frantic. I might take a break from it for a few days and see how I feel then, otherwise maybe I can convince a friend to buy it off me...
Personally, I feel it's the best Halo to date. 343i has surpassed Bungie in my eyes, delivering solid storytelling and an exciting gameplay experience in the campaign, alongside an engaging competitive multiplayer component that will keep me coming back for more.
In addition, I think Spartan Ops is a great idea: it's essentially taking the same, age-old concept of the standard 'weekly TV show' and putting it into video game form - an interesting way to deliver a story and keep the audience engaged for longer than just 'to the end of the campaign'.
All in all, I only have one problem: 343i will have A LOT of high expectations to live up to for Halo 5.