What I feel Halo 4 MP needs is the ability to search for games with good connection. This feature was included with other Halo titles and it's frustrating not to have that option there. I'd be happy to see this added in a patch some time soon.
Also, the glitch on Complex where people are able to get inside the wall and hide is extremely annoying and ruins games of Oddball and Flood on that map. I really enjoy the Oddball game type, but once I see Complex come up everyone votes for it so they can just get into that spot so the enemies can't touch them.