Kraken, I did that too to cut load times (USB Loader GX, I found a 100GB HDD in my sister's dead PC so I said, "why not?"), but for some reason you can't access your Wii Friend Roster in the game (to send invites), and there are some pauses in the online menus, so I tend to stick to the actual game disc. Once I have everyone added I'll probably just use the HDD instead.