It's a good game, it really is.
If you're not going to play online, don't buy it.
The Campaign hardly lasts 20 hours, so it's over-priced for just single player.
This is where multiplayer kicks in. The multiplayer features are good,
but you must sign-up with xbox-live, create account, silver membership (free),
a lot puzzl'in and you're done.
My copy of Halo 2 included a month gold memb.
But I'm not into that right now

.
It's nice to steal a ghost from another Spartan, or Covenant.
You can play as a Spartan or a Covenant.
Dual-wielding weapons is a great thing, easy to use once you've passed 2 Campaign missions.
No, I'm not using a * Xbox controller.
Xbox controllers might be nice, but It's harder to aim, next to that, it has auto-aim, which is rather noobish.
Tide's can change quickly, example:
Slayer: Blue 27, red 52, 20 minutes remaining.
End: Blue 97, Red 100, 3 minutes remaining.