This is a great game and a decent start to a new trilogy of events in the Halo Universe.
Sound is extremely well done, you can definitely feel the power in weapons that should have it. Especially in vehicles like the Warthog which now sounds like a powerhouse, as it should have always sounded.
Music is great as always, though it's too bad they couldn't keep the original composer from past titles as he's done great work in the past for Bungie.
Multiplayer is great fun with a solid progression system that eases you into the game with load outs and unlockables that aren't too expensive or hard to get. You can easily have several different load outs all customized to your play style within the first 10 to 20 levels which should only take you a little over 5 hours to do.
Now where they take a hit in my opinion is Forge. A way to customize your own multiplayer levels and make your own game modes. Unfortunately you aren't given as much freedom as I had hoped we would but none the less the new tools are definitely a big improvement over the old system. But just because we have new tools doesn't mean we're okay with limited Forge maps with small sizes. And making your own custom game mode can be tricky and you'll often find yourself making compromises.
Story (spoiler free) isn't bad. It isn't what you'd come to expect from Bungie but we have all understand that it's not in their hands any more. I feel that the story 343 decided to go with was designed to play out in the span of 3 games. So if anyone out there is disappointed with the ending, think about it for a second. It's the first game in a new trilogy. Halo 1 had you driving a warthog to end the game and you didn't get much feeling of closure until Halo 2 came around to really show us what's what. So when Halo 4 ended and I watched the Legendary ending I knew that there was going to be some heavy stuff going down in Halo 5. Not to mention, that most people don't realize that the campaign continues with Spartan Ops. In a way it replaces Firefight mode (R.I.P sweet prince), but it does it in a way that actually tells a story.
All in all this is a great game. Don't hate on it because it's not Bungie, seriously give it a chance and understand that it's only the beginning to a new series. And everyone knows there are three stages to a story. Introduction of the problem, climax where everything goes to heck, and the resolution where everything becomes alright again.
Good luck 343, I look forward to Halo 5.