Maps And Content Download : Five maps are discussed in the article with some good details. Grab the magazine if you want to read up on these levels. Content Download is definitely going to be a factor in Halo 2. Bungie says you can expect more of everything. Once Halo 2 is on LIVE they want to "keep it fresh and alive and cool and changing it up for our fans."
Vehicles And Boarding : All the classics are here as well as the Banshee (complete with aerial moves a la Crimson Skies) and the Covenant Wraith tank (which, at the time of this article, is still a bit too powerful). The Scorpion tank is slower now and its damage has been reduced a touch.
The article describes the boarding feature as accessible on all vehicles including the Banshee and both variant of tanks. Interestingly, the tank is not technically "boarded" as a player attempting this maneuver latches on to the outside and chucks a grenade in the cockpit thereby vacating any previous occupants of said vehicle and allowing you to commandeer it without hassle.
LIVE Tweaks : Bungie has created a random matchmaking system that allows you to find a decent game without scrolling through endless server lists. Thankfully, Halo 2 will allow you to compare your ranking within your Friend's List so you can see how good you are within your circle instead of how crappy you are in the world rankings. Keepin' it personal.
The article is a great read and I highly recommend you pick up the October issue of Official Xbox Magazine (the one with Master Chief's face plastered on the cover). Until November 9th...