They really need to go back to the old school Halo-vibe and ditch jetpacks, shielding, and all of that bs.
Halo 3 and previous were great because the games were controlled by weapons/vehicles, knowing the map and playing it to your advantage, and raw quick reactions by players. That's it. Once you throw jetpacks and all of the other crap in, you have some Unreal Tournament bastardization clusterfuck.
Not only that, but the damn maps in Reach weren't even built to accompany the perks, mostly because it was impossible because of how many, very different, perks there were. The "map control" aspect of the first 3 games, where blue team might have high tower on lock for example, is thrown out the window when red team can jet pack up in 2 seconds or sprint over to it in 5. Halo has also had this interesting team dynamic where parts of the map control shift back and forth, but it's much more blurry and discombobulated in Reach.
Reach was a good game, but not a good Halo game, at least in multiplayer. If Halo 1-3 never existed, it wouldn't have been judged against them... but alas, they do. Keep classes/perks/abilities out of Halo, imo. It's "CoD-fying" something unique and tried-and-true already.
Edit: The preview mentions making master chief feel strong and elite like in the books, which sounds awesome! One of my primary complaints... Just hoping they can keep that in single player, and make multiplayer it's own thing. Not a tribes/UT/CoD crazytown mix.