Let's get back to the basics!
A lot of familiar feelings returned with ODST, almost immediately as I got a feel for the revamped pistol. This was obviously a big step in the direction of Halo 1, as die-hard original fans were furious with the deletion of the precious zoom option in Halos 2 and 3. The headshot is back, and with a vengeance. You can even zoom with the SMG, which I found to be satisfying as well. Both weapons are silenced(!). On top of these default weapons you will encounter a truckload of familiar weapons from the Halo universe. If you start taking hits and lose your shields, you must take cover before you start taking actual health damage, and being as you are no longer a Spartan, you must be wary of jumping from high spots. Take some body damage and seek out a health kit. Suddenly you realize you are no longer an unstoppable spartan, able to jump and melee and kill anything with a single glance. This feeling of mortality forces you to play more conservatively, and you start feeling more human almost immediately. As all these changes set in, you remember what it felt like to conquer difficult levels on Legendary with your best friends, and you remember what it was like before you associated the Master Chief with the grating voices of a sea of taunting eight-year-olds. Ugh.
ODST has no competitive multiplayer. Let me say that again, just in case you missed it. NO COMPETITIVE MULTIPLAYER. You must play with your friends like we all used to and battle the Covenant, old school status. If you are one of those whiny eight-year-olds, or you just want to remember what competitive Spartan battling used to be like, you can pop in the second disk, included with ODST, and play the Halo 3 multiplayer as an added bonus. This includes all the DLC available for Halo 3 to date, as well as a few new maps including a remake of Halo 2's Midship. The multiplayer on ODST is called Firefight, and is set up similar to Horde on Gears of War 2. In case you aren't familiar with this game mode, you basically hang out on a Normandy-style map and try to survive wave after wave of enemies until you run out of lives. Your resources and health packs are limited so you have to give it all you've got! Personally I love this mode as it gets exciting and extremely difficult. One disadvantage to this mode is the lack of Matchmaking. If you want help from your friends, call em up and get em online. You can play up to four people together at once but you can only house two on a single Xbox at once. This I can deal with. I have found most encounters on previous online Halo games to be unsavory, where instead of battling Covenant, I was forced to battle wave after wave of racist, trash-talking cretins. Sticks and stones, I know, but it really wears away at you after awhile, no matter how stony your disposition is.
Bottom line is ODST is a shift in the direction of Halo 1, and a far shout from the last two Halo games. The only thing that remains is the same familiar control scheme and a plethora of cool weapons. You now have an alternate view mode called Visr Mode, which is like a night vision combined with colored outlines kinda like GRAW. The graphics kick the crap out of any previous Halo games, which I found to be awesome as well.
Take it or leave it, ODST is NOT Halo 3. It feels much more like the old school.
Rob