"Wiimote Lag" may or may not exist depending on what you are refering to ... If you're talking about lag in communication, this is no worse than the lag caused by the PS3/XBox 360 controller and you probably won't notice this unless you have something set up incorrectly. There is some lag with the Wiimote when you are performing gestures because a certain ammount of motion has to exist in order to trigger the action the gesture represents; for example, you have to swing the wiimote for a 1/4 of a second (to pick a number) in order for your Mii in Wii Sports to swing their tennis racket.
In a game like Metroid Prime 3, which doesn't rely on motion controlls as heavily as other games, the lag should be no worse than a PS3 or XBox 360 game; and when you factor in the added speed and accuracy of the direct pointing of the Wiimote it should be far better than a PS3 or XBox 360 game.