[quote name='grap3fruitman']Uh, no it's not. If you're using wireless you will have a much larger ping that will negatively affect the gameplay of other players. Particularly in games that need tighter timing, like fighters.[/quote]
I don't play fighters online (I'd imagine getting as low a ping as possible for those really does help) but I've played a ton of Left 4 Dead and Team Fortress 2 via wi-fi when I'm on my laptop and don't get any sort of lag (unless there's some issues on the server side of course) and my ping rarely climbs above 50-60 which is more than good enough to play those games. I use wired whenever possible (like when I'm on my desktop) but when I'm not near my router/modem, wi-fi works just fine for me in games. Can't imagine it being worse on the 360. Guess I'm lucky to have a fast connection and a good router.