ODST has it's flaws. But at the end of the day it's a fun game and you could do alot worse than buying it.
Halo 3 ODST play much like Halo 3. More like Halo: Combat Evolved, actually. Gone is dual wielding and deployable equipment. Fall damage and the original health model are back. For those unfamiliar with Combat Evolved there a recharging health system called "stamina". Take damage and if you wait long enough with out taking any more you as good as new. If you take to much you'll start taking damage on a base health bar and the only to recover it is finding health packs.
To some this will feel like a throw back. And Bungie has done these things to make you feel more vulnerable. Although to many, this probably feel more like a step backward. What ever the case the game still plays much like past Halos and is about as enjoyable. However, considering the changes made to make you feel vulnerable, the ability to wield the powerful gravity hammer and rip turret contradict the feeling of weakness at times. It's not a big deal and it does make the game more fun but one has to wonder why take some abilities but not others.
ODST's campaign has you playing as "the Rookie", a lone... ODST(Orbital Drop Shock Trooper. The baddes bad asses the UNSC has to offer aside from Spartans like the Master Chief). You wake up six hours after a combat drop into the night time city of New Mombasa. Alone and seperated from your squad. Your objective is to find clues that will help you decipher the mystery of what happened to your squad.
You can think of the night time level here you play as the rookie as a hub world. In this level you can search around to find clues which activate levels that take place in day time from the perspective of your other squad mates.
What with the silenced SMG, the lonely atmophere and darkness of the night time levels you may get the idea that ODST has a new focus on stealth. Well, it doesn't really. If you shoot at an enemy(with a silenced weapon or not) they and it's comrades will most likely notice you right off the bat. You can sneak around enemies some times and plot routes avoiding enemies using your map, but it's often less time consuming and more fun to take a more direct approach to where you want to go in the night time city be there covenant in your way or not.
If you had any expectation that New Mombasa is open world, forget it(the fans seem to have goten' the wrong idea). It's really a big hub world, nothing more. The only activity beyond searching for the clues is finding audio logs. Audio logs contain story presented like a radio drama. It's worth looking for them if you're interested, it really completes the narrative and gives you much needed insight on some of the game's mysteries.
ODST can sort of be open ended. After completing the first two flash back missions the next three can be tackeled in any order you like. But you likely will just go to the ones that are closest to you and that should be the order you take them as thats the best order they flow chronologically in the story. Theres really benefit in viewing them outside of that order.
Navigating through the city couldnt be any easier. By pressing up on the d-pad navigation points will show up leading you to where the next clue is. You have an onscreen compass right above your health bar and objectives will be displayed there too. You can also check your map to see where you are and where exactly you want to go and if all that wasn't enough street sign will actively point you in the right direction as well as warn you if enemies are ahead. Unfortunately, the city is dark enough to where during the nigh time level you will pretty much will always be using the VISR mode making if difficult to even view the illuminated signs.
The VISR mode another addition to ODST. It's a vission mode that sort of works like night vision goggles. They bright of the dark street of the city and cast outlines of points of interest. Red outlines on enemies, green of friendlies, blue of vehicles, weapons and grenades and yellow on special objects like items that activate the flashback levels.
And for the flash back levels. These levels have you playing as other members of the squad during earlier parts of the day. These levels play more like the Halo you know. More action oriented and linear.
All in all the campaign is about five to six hours on your first run. My first run was on Legendary in 4-player co-op. It took about six hours. One of my more recent runs on single player on heroic difficuly took me about five hours. So it's a little shorter than Halo 3, but not significantly. As I said you can do up to 4-players co-operatively and you have four difficulties to choose from. Legendary is a must for co-op.
Aside from campaign ODST also offers a new mode dubbed FIrefight. Here you fight endless waves of covenant where you can have up to four players participate. Most of firefight's maps are available right off the bat but a few require that you complete some of the campaign levels to get them. Once you have them all though theres a total of ten maps(although two of them are just night time version of already existing maps). Similarly you can unlock characters to play as in Firefight through completing certain tasks in campaign.
While FIrefight is a familiar concept it does plenty to seperate itself from the crowd. In firefight plays have a shared pool of lives meaning one player's death effects everyone. As the game progresses to difficulty skulls are activated. And certain maps have certain enemies. For instance the night time maps will have egineer providing over sields for near by enemies at times. Some of the bigger maps will see Wraith tanks dropped and other maps will have occasional Jackal snipers shooting from rooftops at you. This helps give each map it's own identity.
There are some obvious features missing though. Matchmaiking chief among them. And unfortunately if just player lags out or quits the game automatically ends.
Halo 3 ODST includes many feature found in Halo 3. You can save films of previous and take screen shots from them and put them up in your file share. Unfortunately like Halo 3's campaign you can not make short film clips from campaign and firefight matches.
ODST also runs off the same engine that powered Halo 3. So the game looks good, but not especially impressive from a technical stand point but the art direction on the other hand is very impressive with the surprisingly varying locales and moody atmosphere. However, human faces are just as unimpressive as they were in Halo 3 save for the characters Buck and Dare both of which were modeled after real world actors.
The voice acting is of the same quality of Halo 3. Pretty good. And the music is of the same par set by previous Halo games. Freaking amazing.
ODST includes a second disc dubbed "Halo 3: Mythic". This disc contains the complete competetive multiplayer component of Halo 3(hence the 3 in Halo 3 ODST). It includes Everything from Halo 3 except the campaign. So you have the match making, custom games, forge and theater modes. On top of that all the DLC maps and title updates are on disc as well as three new unreleased maps.
Theres not much I could say about the Halo 3 multiplayer that hasn't already been said. It's a well crafted, well balanced multiplayer game and arguably the best you'll find on the 360. Regardless it's largely something thats been around for a while and most of the people who are buying ODST likely already have most of this content. It's a good deal for the people who never purchased the maps or never purchased Halo 3 itself but to the Halo 3 fans who've been playing up till now and have all the DLC the only thing in it for them are the three new maps and the hard drive space they'll be freeing up.
ODST has it's flaws. The campaign is fun and fresh but while the hub world was an interesting idea it was poirly executed. You can spend tons of time fighting off hordes of covenant in Firefight but with out match making it's not going to tide alot of people for too long. The Halo 3: Mythic disc contains one of the best competetive multiplayer games to ever grace the x-box 360 but it's hard to imagine too many people don't already have Halo 3. But at the end of the day it's a fun game and you could do alot worse than buying it.