It's hardly worth it at all... I'd have thought learning how to launch properly would be a much better way of going about drag racing. Launch control is usually used to build boost before launching, but since you are missing a turbo or two that's sort of irrelevant.
Not sure what you mean about using it in place of the standard rev limiter? That's there to protect the engine anyway.
What do you mean you like to rev to 7,000rpm? While driving?
People usually fit the Bee*R things for the noise they make rather than for any real quantifiable benefit.