To answer the question, adjusting the port settings and getting the max out of your connection to a server weigh on your multiplayer experience. For aggressive players (hardcore), the small amount of lag in the ST could punish the fun factor if those aren't ideal during twitch shooting or sports games online. For normal players - you won't notice much...you'll just get killed frequently like you usually do and laugh.
On the whole, you may have to adjust your timing a little for jumps and steering and the like. On shooting games...I found that I had to switch to more stealth and sniping than run and gunning. That extra split second on face to face trigger pulls went against me more than the law of averages allows. That's actually a bit more challenging - hence more fun.