Is it auto or manual?
Mine is a manual, so all it does is change the linearity of the accelerator pedal, so you get more throttle for less movement.
I'm told it also changes the steering weight, but that isn't particularly noticeable.
Only trouble I find with it is that it makes it a little jerky round town at low gear/low speeds, so its back to comfort for that.
If you have an auto box it makes changes to the way that reacts, but I have no experience of that in a Z, so will leave to others to comment.