After testing this for a while I found some stuff I can come up with.
ODST details:
1. VISR mode appears to work a lot better than before, outlines showing more visible than when ODST first came to MCC.
2. I don't know if it was only me, but there was a rapid fire bug that caused a waste of ammo on certain weapons, but also prevented the Spartan Laser and Plasma Pistol to charge their shots. It appears to be fixed now and has quite helped a lot on Legendary runs.
3. It is good to see ODST Firefight back and way better than before. Although it can still be hard to run through it once the Catch skull is on, one can still enjoy it. Thanks for adding the AR and BR back to Firefight too.
4. After unlocking the ODST characters I noticed there are 4 locked stuff in the customization. Why can't these be unlocked?
Halo 3 details:
1. The new skins, although few, look cool. But in my opinion both the AR and the Magnum are basically using the CE skins adapted to Halo 3. The BR however looks nice with all new skins.
2. I'm playing the Spanish version of the game (LATAM Spanish) and now I see certain names have changed. For example, the SMG has always been called "Subfúsil", but now it is called "Metralleta" for some reason. And the Mauler now keeps it's original name instead of "Aplastador". What made the change?
3. The Brute Plasma Rifle appears to behave more like it's Halo 2 counterpart. Please keep it that way.
4. The Suppressed SMG works nice and feels balanced the way it is. However, in my opinion it's position looks odd compared to the default SMG.
5. The Auto-Mag doesn't feel automatic and fires like a normal Magnum, just with zoom, more ammo and less damage.
6. None of the two ODST weapons can be dual wielded. I'd keep it that way, or else both will feel overpowered.