I had progressive H&Rs installed in my old car, which you can see in the little picture next to my name.

They worked great!

H&Rs are a german brand and widely used in Mercedes, BMW, etc etc, as well as on the racing circuit. If you see the Mercedes at the 24 hours of LeManns they use H&R..

Anyway yeah they are awesome. And progressive is the way to go. If I can explain it a little bit better, if you picture the spring, they are softer near the top, and progressively get stiffer and harder as you move down.. As you go over small bumps and around turns, etc, the spring is softer the smaller the move. The more weight that gets pushed down on it, the harder it resists.

This is what allows it to give you a comfy ride, but sporty handling. Small bumps will be as unnoticable as if you had regular springs, but when you really work it, and put weight on the springs from flying around a turn, they get stiffer and give in less.