I picked up a pristine used Wavebird for 45 bucks yesterday and so far it totally lives up to the hype. Never tried one before, but I can't detect lag and the controls feel identical to the original GameCube pads. The only nitpick is the on/off switch, because we might accidentally leave it on after playing. The LED light is prominent, though, so hopefully it won't be a problem.
Totally worth it to get rid of yet another mess of wires.