I had the KW Sleeve kit on the track. It is ok.. I wanted to set my ride height higher than the springs out at the time to maintain shock travel. Eibach ProKit had a higher height too but it is too soft as many have said.
The problem with any spring kit is that you lose shock travel when you go lower and the stock shock can not keep up with the increased spring rate of the aftermarket springs. You end up with an underdamped ride and bounciness over sharp bumps. The worst is the floating sensation as you corner, you need to let the car settle in the corner before you feel confident and planted. Also, ANY lowering spring on the stock shock accelerates wear on the shock and reduces the life of the shock.
But, Swift has recently released their Swift Spec R springs. They don't lower the car that much so it maintains shock travel, it is a linear spring to reduce the floating sensation and Swift quality is top notch for springs. This might be a good choice for people wanting performance springs. Maybe even better than Dinan!
That said, I sold my KW sleeves for KW coilovers. Very satisfied with them. Removes the suspension's weakness which is the stock shocks.