Picked up my preorder of Halo ODST last Thursday and have been playing it since. I played through the campaign in a couple of days. It's fairly short, but with the achievements there are a lot of replayability. There's a lot of counter achievements ala Gears of War 2 where you need to do something in a single level or specific level enough times. I haven't gotten all achievements in Halo 3, but in ODST it seems more likely, even though there are some challenging Vidmaster achievements.

Overall, since I am a fan of Halo 3, I like this game. I played it on Heroic and I definitely felt weaker than Master Chief, but there is still the same recharge shield mechanic. Ammo is a lot more sparse and you'll find yourself scrounging for the Carbine and so on. I won't turn this into a review, so to sum it up I'll say that I am very happy with my purchase, but the singleplayer was not as epic as I wanted. I did not care for the other characters. The dialogue between characters, the love romance between Buck and Dare, is stupid. I'm the last to complain about story, because I rarely care, but having played every FPS Halo game so far, I'm so used to shooting Brutes, Jackals and Grunts. A better story and more enemies (though it might not fit the Halo canon) would have helped it, especially with the campaign being rather short. Then again, playing the game again to find audio files and get achievements on a lower difficulty made it a lot more fun for me, so maybe you shouldn't play it on Heroic first as I did. Then again it's fun because you're more like Master Chief, and maybe that's what I really want.

Firefight is great, giving you a typical Horde-ish mode, but with the gameplay elements of Halo that makes it fast-paced and focused on multikills. I'm also a fan of Halo 3's multiplayer, so it's great that the game comes with a disc with the Halo 3 multiplayer and all maps. Not only do I get three new maps, but I also get to delete the old maps from my HDD and play them from the disc instead. My only problem is that the two discs aren't treated as two discs should be. The second disc is just placed right on top of the other, and being very OCD with scratches I really don't like that...

I guess this kind of turned into a review, but hey. Reading is fun.