It just adds weight. (At least that's what I'm going to continue to tell myself so I don't feel bad for not having it.

)
I've never seen the weight of the Zlink parts, but by the looks of it it could easily be 30lbs.
I had a loaner 2015 1LT cruze without Zlink, compared to my 2012 1LT with there was a difference. On rough roads with lots of potholes the z-link really smooths out the side to side motion in the rear. driving the same road back to back I could drive my zlink car about 20mph faster before the road seemed as rough. driving in corners, initial steer in seemed slightly more responsive as well, though this difference was less pronounced. to me it really is about ride comfort more than handling. make sense its standard on the Buick verano.
Now owning a sonic LTZ with larger 17in wheels vs my cruze 16in, as well as the sonic shorter wheel base you feel allot more bumps in the road. The difference I notice most is on rough roads, there is WAY more side to side action in the back than my Zlink equipped cruze. If I was buying another cruze, I would not want one without the Zlink.