In terms of the main menu for level selection and options and stuff? I guess it would've been nice to use some concept art backgrounds like Reach does, but I get the sense 343 wanted to keep the classic title screen with the Halo ring in the background, and really, when you get down to it, the game doesn't really have many of the features a UI like Reach's is built around. There aren't nearly as many customization options as have been added over the years, there's no theater menu, no customizable character, and the entirety of the multiplayer aspect of the game is in Reach's engine, I don't think there's a whole lot to add. So the UI is definitely not as full as in more recent games, but Id don't think it can be with the limited set of features available. Goes to show how much the series has added in 10 years.