So I bought this game and it definitely has its improvements over Halo3, but also has some major disappointments as well.
The thing thats new in this game that I really like is the armor specials, which were kind of in Halo3 but came in the form of powerups picked up throughout the maps. In Halo: Reach however the powerup stays with you once picked up and allows you to use it repeatedly. Abilities like Fast sprinting, jetpacks for short flight (really awesome if you like to snipe), temporary invincibility, & bubble shields that recharge your player shield and health. It added a whole new angle on battle strategy that I really enjoyed.
That being said the game does have its drawbacks when compared to Halo3, for one...there is no dual wielding system at all. And some of the weapons featured in the game are no means powerful by themselves. Also the story line doesnt seem to add up to the other games...for example some of the weapons seem to be modified and act far more advanced than the weaponry in Halo1-3 which is kinda lame because Halo: Reach is a prequel to Halo1.
Special armor abilities have their drawbacks as well....for example if you activate temporary invincibility enemies have a tendency to stand there and wait for it to run out before capping you in the head. That or they throw a grenade at you perfectly timed to detonate as soon as you come out of it...so this ability is really only useful if say a rocket is approaching your face or a plasma grenade is already stuck on you. Sprinting ability does not allow you to fire your weapon throw grenades..or basically anything else for that matter....but it does seem to add some dmg to the melee hits. The jetpack has a short range of flight and using it in front of enemies gives them a nice slow moving airborne target to practice on.
It took me one day to beat this game start to finish on Heroic difficulty with some of the skull multipliers on increasing the difficulty to get a higher score out of it. Which was pretty disappointing and honestly a week later now...I am back to playing FFXI shooting for Lvl-85 on all my jobs because im semi-bored with Halo: Reach already. Storyline was kind of weak and annoying at points, like it was just WAY too dramatic for its own good, and often found myself mashing the controller buttons in attempt to skip the cutscenes.
Some of the things I DO like alot about it are the new game modes like Firefight, where basically you can team up or go solo against hordes of covenant until you have no choice but to die, but the object is survival. Another is the enemy A.I. seems highly revamped in this game, no longer are the grunts stupid and easy to pick off on the harder difficulties. These things will not wait behind cover so you can run around punching them in the face, they will strategically surround you or hit you with grenades pretty quick. Campaign mode is pretty easy to memorize, ie; the mobs always spawn in the same spots and you can know exactly when and where theyre going to pop out so your already aiming there...thats kind of a drawback but with the increased AI actions it kind of accounts for that.
Currently im playing thru campaign on legendary and its kinda b/s. For example an elite with an energy sword you can shoot in the face like 20 times and he runs up and wacks you once when you've got nowhere to run to and you die lol. Whee time to start the whole fight over again
I'd say this is probably a game you should rent for about a week, and if you can still sit down and play it after that without getting bored...then its worth picking up.
Edit: Oh almost forgot....I wont drop a spoiler but the ending really sucks @$$. My friend and I repeated it 3 times thinking we had screwed something up but nope....thats just how it ends.