On everyday street cars, the benefits of the added stiffness outweigh any differential concerns. It is important to note that the rear sway bar shouldn't be added without the front sway bar already in place. I hear that handing will be all over the place if the car only has just the rear bar. The front sway bar may be installed just fine without the rear was installed as well. The first step in performing the installation is to obtain all the necessary parts.
Pelican Parts can provide all of the parts to do the job right.
The factory sway bars are sometimes difficult to come by, however, Weltmeister makes a really great aftermarket bar. We are currently having the rear sway bar brackets and reinforcement plates manufactured to the original specs, at reduced factory prices. Drop us a line if you want to order a complete installation kit for your car. The only difficult part about the installation is welding the brackets onto the car. The brackets fit on the underside of the trunk of the car.