The region selection update can't come soon enough. I hate quick-matching into further-away regions, especially Northern Europe (I'm East US).
The ODST Firefight experience in matchmaking can be pretty dreadful/restrictive when not in your own region. Some things you can normally do on your own (assassinate Chieftains, battle Hunters in CQC), it's often suicidal to try to do here because you are not always shown what direction they actually face, sometimes for a good while.
Recon Slayer could use a permanent place in Halo 3, be it mixed in with other gametypes or whatever other way you can do it. It's a pretty fantastic way to play.