Another flaw not mentioned with the controller was the afterthought called a Z button. Thankfully it wasn't used much at all since it is very poorly positioned to press during gameplay.
Play many racing games? The entire point of a analog trigger for a racing game is to replicate the functions of the brake and gas pedals in a vehicle. But the very design of the GameCube's triggers with their two stage design makes them undesirable for one of the primary purposes they exist for on modern controllers in the first place. You can't smoothly manipulate them through their full range of motion. The GameCube triggers are essentially either fully depressed, half depressed, or fully released. It's almost now a digital control rather than a analog control.
Even worse than that (I've never thought analog control of braking and accelerating with a gamepad was a very effective idea, the range of motion is just too small), they're also uncomfortable for extended use. Play a racing game for a decent length of time and I suspect you'll start to find keeping the right trigger engaged uncomfortable. Never been a problem on a Microsoft controller.
I agree that it is a minor issue. But still it's one worth mentioning. The occasional game makes excellent use of controller rumble to enhance the experience and sometimes it is even an important feature in a game. In several 3D Zelda's, for instance, it is used as a hint system. You might be walking over a spot with an underground cavern and the controller will rumble to tell you that the ground in that area is weak so the player knows they can place a bomb to open up a passage.
You lose such features with the WaveBird.