Yeah, I used to play america's army and couldn't figure out why I had such low scores and would get killed so easily. Then one night I snuck up on an enemy soldier, emptied an entire clip into him, POOF he disappeared and reappeared 3' to the left where he shot and killed me. Turns out he was running a quad core hi perf machine with a net speed of 4 times what I was. It turned out I was running a full second and a half behind everyone else. It turned out that by the time my machine downloaded the data of all the other players, they'd already moved so I could never shoot and kill anyone.
OH, and at the time, I wasn't running the bare minimum setup. I was a couple of notches above that.
Moral of the story is: if it is a fast paced game, don't bother unless you have a top, or close to the top, notch machine and net access.....