A few days ago I installed the Steeda strut tower brace and larger rear sway bar; I can not speak as to how the two items perform individually, but as a pair, I can attest to the fact that the improvement is amazing. I took my girlfriend on a winding road this morning that we took just last week and she stated that she felt much more confident this time, even though I made sure that we where taking the curves at the same speed as before. I felt the my FFH was a great handling car as it came from the factory with the 18" wheels and the LS2 tires, but now it is better than I could have ever hoped for, I just love it. I have tried to determine if the ride is any harsher on different road surfaces, but after much testing, I just can't say for sure one way or another, so I guess that I am saying that the answer is "no" to that.
I installed the strut tower brace myself in about 5 minutes, but since there was now central location to jack up the rear of the car as a whole, I took it to a local garage and we installed the rear sway bar together on the rack; I would not recommend trying to install the sway bar by yourself on the ground, it would be very frustrating, but doable.
The strut tower brace is $120 dollars and the rear sway bar is $150 dollars, money well spent in my opinion.