you guys have to remember if your playing online and you have a high latency things like this will happen IE:
"Shooting people and they dont die"
This happens cause your lagging out on your connection, the system is not regestering a hit because it cant determine the time you fired from the time the bullet would have hit the person.
"People Jumping around the map"
This is caused when the data from the server is backed up and gets your system in bursts hense why you see a vanishing player re-appear a few feet from where he was standing, this can also be a reason why your shots dont hit said player.
"Not regestering your GS"
This is caused by a glitch in the 360 console and it usually client baised IE: "Only you cant see it"
you also have to realize that this is a new game and of course there are going to be bugs especially in a launch so massive as this one, give it time and they will patch it out