Here's an my personal opinion for anyone considering buying this kit.

A little backstory:
I live in Puerto Rico. Mostly clear and sunny all year round. However, the roads around here aren't even worth the asphalt they are paved with. Potholes everywhere. I wanted to improve the handling of my Mustang, but the more I drive around here, the more I dread ever considering lowering the car.
So I skipped the lowering aspect of improving the handling and went straight to sway bar stiffening. Went with the Eibach kit.

The rear swaybar was relatively easy to install. I used ramps and didn't even need to take the wheels off. The front bar, however, was a pain to reach and after a few tries, I gave up and decided to take it to a mechanic.

I was driving to the mechanic with the rear Eibach bar, and the stock front bar on, so I did a few swerves and slaloms thinking that just the rear bar would make a difference and I didn't notice any difference in the response/bodyroll of the car. I felt like I wasted my money, but I was halfway to the mechanic, and the kit was already bought so on I went.
The mechanic installed the front bar without problems and put it on the middle hole for neutral steering, as I requested.
On the way back I did a few swerves again and WOW! what a difference!! The car felt planted and didn't roll as much. The front bar was a necessary component for this kit to work. Definitely worth the money if you want to improve the handling of your ride, but are thinking of forsaking the lowering.

And no, I don't autocross, track or race the car at all, so I can't tell you if it would make a difference there. I bet it would, but maybe not that much. I don't think it would help much in the long, sweeping corners, since I have the stock 18" wheels and tires, but I'm sure I could take "successive" corners much better that stock.
I'll probably never know...

So, short version:
Good kit for the money. Buy the whole kit. Rear swaybars alone do jack squat. The stock front bar has to go.

 

Good info! Is that the same as the FRPP swaybar kit?

 

I believe it is, but the FRPP pack costs about $75-$100 more than this kit. I read that the bars are the same diameter and the only changes are the blue paint and the rear bar hanger...link thingies are not billet like the Eibach kit.

Maybe the FRPP kit is warrantied and the Eibach kit is not.

 

I have been debating this Eibach Kit since i lowered my GT on FRPP "K" Springs.. I am just not positive i want to spend $350+ on it just yet.. I want more power first.

 

Ok, guys. A bit of an update.

I drove the car through some mountain twists and there is definitely a noticeable improvement. I could tackle corners that usually required me to slow down to a crawl or the car's front bumper would end up in the mural. I know you must probably be thinking that it is some placebo effect, but I honestly wasn't expecting much difference at all. But it IS there. You can feel it.

Anyway, it seems now I may need some help from other people who have this kit.
Mine is starting to "crunk" a little from the rear bar (the one that I installed myself; probably incorrectly). The front bar is dead silent. What are the common causes of this? Did I go light on the bushing grease? I went back under the car and re tightened everything down, but it's still there.

Any help appreciated.

 

How big is that Eibach rear bar? I put on Steeda's smaller rear bar and it made a HUGE difference IMO.

You might try re-greasing the rear bushings, I can't think of anything else that would cause that unless you installed upside down or something.