Keep in mind that, especially for performance cars, the instant torque and low center of gravity (because those cells can go in the floor) really helps.

Yes, the added weight is bad for handling which is a shame especially in a car like this.

The weight savings aren't that big of a deal, they do that in every car and it's mostly marketing. But if you're one of those brands that can sell the same car, but use some fancy metals and such for a 50k markup, why would you not.