I started Halo 3: ODST about 8 hours ago and the game was so incredible that I just went and finished it in one single night. I just ended the campaign and the truth is that I believe I might actually have enough time to finish the entire series before I travel. Tomorrow in the afternoon I'll start Reach and do what I can to finish it in a couple of days. I think it might be possible.
It bothers me a little that Bungie changes the way the weapons work so much for each game. In ODST I found myself comfortable with the Plasma Rifle and Carbine most of the times, the Pistol is good as well but God, the Assault Rifle is way too weak to kill even at mid-distance. The truth is that I believe the best weapon balance in the series is in Reach where you can actually kill anything with any weapon.
I also find ODST's plot more interesting than Halo 3's which I finished last night, but I love the entire series, I wanna play some firefight and multiplayer matches with my friends before going out of the country, but I guess it won't be possible. Anyway, that's the quick update of the night. I finished ODST and will start Reach tomorrow.