Gotta say I'm not impressed with the UI at all. The menus on the start screen, there's seriously no way to go back? Ooops, I clicked the wrong button, now I gotta enter all the way into the game, then quit the game, then back to the main menu because I accidentally pressed the wrong button.
Also makes it so I can't explore all the different menu options to see about the different game modes. There's also no instructions, controller map to show what buttons do, loading screens that give you tips to show you what the different power ups / or weapons types are, no explanation of the different icons, game modes, etc.