Even if Wifi is setup correctly with MAC and WPA, there is still issues to face with a media centre setup.
Other people with wireless settings can hamper your experience, it happens around here when the latest netgear devices flood the whole wifi network when transferring large files.
Who wants a media centre with hiccups while watching the movie?
I prefer a dedicated ethernet without those interruptions for my media centre, however I can have both if required and I have to expose my blue cable in part of the room, without the privilege of being able to hide it in the wall.