I'm not sure if I would call it a beast. Anyone can install one themselves with only a few drill holes, so it's not like it's heavy. Certainly not enough to affect gas mileage.
If you want to look at it that way, why not say that since it sticks up an inch higher than the roof that it might cause wind resistance and lower mileage?
It's all just a preference if you like the look, or don't.