Sorry for the minor resurrection, but my brother just got this for his birthday last week, and I've kind of...shall we say..."borrowed" it from him since then.
I'm not as into Halo as a lot of people are, I'm more of a Call to Duty guy myself, but I still really like the Haloverse quite a bit, and I've enjoyed the games, for the most part. I'm finding that I'm really liking
ODST, I don't know if it's the atmosphere or the mood or what. It's a fairly short campaign, but this is one of those cases where quality wins out over quantity. Playing as an ODST just feels more fulfilling to me than playing as the Master Chief; I guess it's because ODSTs are just regular human beings, so there's more of a challenge to it.
I have to agree with others about the music. Running around the dark streets of New Mombasa and listening to that lone saxophone crooning is just awesome.
And of course, it doesn't hurt that Nathan Fillion, Adam Baldwin, and Alan Tudyk play three of the Rookie's four squadmates.

I'd really like to see another game starring this squad in the future, though there probably isn't much else for them to do between the end of
ODST and the end of
Halo 3...