Their updates of the CE Anniversary maps, questionable weapon placement on Beaver Creek aside, were pretty good. Prisoner and Hang em' High both fantastically benefited from additional routes to high ground.
They have shown a decent ability with the last Halo 2 pack and Anniversary to update existing maps for new generations, but the stuff they did from the ground up with Reach left a lot to be desired. I don't have super high expectations for them in Halo 4 as a result. I already have significant issues with how they've structured Dominion, but that's probably a separate issue.
I check the traffic for the dumb site I run every once in a while and those stats include search terms that lead people to it. Usually it's South Americans and Eastern Europeans looking for a Halo 4 trial (why am I the first result for "Halo 4" on an Italy-based search engine, exactly?), but occasionally I get some good stuff. Today, it's an instance of "halo 4 global ordinance pattern?" and "global ordnance drop halo 4" and "how to get the bianary rifle more often in ordanance drops." People are asking Jeeves and the Googles how a fundamental gameplay system works. If there is any reliable indication that the huddled masses don't understand something, it's this.