Speaking from experience, (my car has the ES bushings) they really don't feel as if they mess with the suspension, the spring rates, or the suspension travel. After I installed all my bushings I put the car on jackstands, and jacked the wheel through its whole range of travel, and nothing looked out of whack.
Just a note though, I installed all my own bushings EXCEPT the trailing arm bushings. I tried to burn them out with a propane torch, and i tried cutting them out with a Sawzall. Nothing worked. Since I had the arms off the car, I decided to have a shop have a go. I went to East Coast Custom Ridez in Worcester, and they finnally were able to get them out, and pressed in, after an Oxy/Acc torch and a die-grinder.
One thing that you may notice, is that with a small rear bar (stock EX or none) snap oversteer can sometimes be a problem. In daily or spirited driving this really isn't a problem, but I auto-x, and mid-to high speed hard turns sometimes lead the rear end to step out a bit.
Looking to upgrade to machined lower's in the future.