Personally, I feel like they are just a novelty. They don't really distort the view, except for macro shots through the wave.
For me, if I'd the space for the wave front, I'd rather just get a rectangular tank that was just was long, just as tall, and as wide(front to back) as the widest point on the waver front.
For a 120g or something like that you'd get a bigger tank, and you wouldn't be paying for the novelty of a wave front.