Halo 4 multiplayer saw a rather dramatic overhaul IMHO of the traditional area style shooter that halo 1 to Reach. It introduced several new dynamics to the multiplayer experience that where not present before in the franchise, however followed by the release of Black Ops II a week later population of the games has and is still rapidly decreasing.

Custom loadouts: the ability to choose the starting weapons exposes several issues in the sandbox of halo 4 weapons with several weapons: the plasma pistol, plasma grenades, boltshot (all Promethean weapons as well really) and DMR these i admit cherry picked but they have a great affect on the general gameplay.

The boltshot and the DMR represent on spawn power weapons with the boltshot far more effective that several power weapons. The DMR shares the same issues it had in reach along with the new flinch mechanic which eliminates the two people enter one leaves aspect present in competitive halo. Finally the plasma pistol & nades combo which unbalances BTB matches completely.

Vehicles: apart from artistic and audio choices for the vehicles usable in multiplayer only two present real issues from a gameplay perspectives the Gauss hog and the Mantis. The gauss hog mainly due to the ease of usage and destructive power which even after post patch is still rather unbalanced form a gameplay stand point. The mantis also suffers from this general broken nature as well this is quite noticble in a majority of BTB games specifically the classic style game type with no AA's, its shield means that it is capable of surviving multiple power weapons shots most likley killing the attacker first although this is the case for several other vehicle's such as the wraith and the scorpion the mantis realistically doesn't owing to the ability to use both armaments at the operator's digression which is dramatically different to most other vehicles (the hornet could be argued with this case as well but it was relatively easy to destroy)

these are just samples of the issue that i feel halo 4 has excluding Promethean weapons, 14 trial for majestic map pack, poor dlc integration (not well done since 3) and generally poor poor multiplayer management (perks, ordinance and the list goes on) in general if people would like my opinions on these i'll gladly post them.

So what do you think halo 4 multiplayer did well?

Note: I still play halo 4 its a decent FPS but its pretending to be something its not which is a halo game