Mine was the first to be fitted with Nitrons. I have the setup which was designed to be slightly firmer than original.
I think this replaced the suspension which was fitted in the factory & 80,000 miles old...so it was well worn & this will have coloured the below comparison.
I went for a set to replace my tired old suspension & did not initially realise it was an upgrade package
The Nitrons are firmer so help to keep the car flatter when cornering. Somehow they are also able to absorb smaller bumps more comfortably. You can adjust the ride height by turning the spring mount around the strut. They provide a tool for this although Nitron's engineer preferred a drill bit!
You can also adjust the damper's firmness. As Gazza pointed out, the adjustment is at the top of the strut so it is kept well out of the way of any road dirt. I did not touch my damper adjustment for well over 2 years but it adjusted very freely with nice positive clicks when I did so. I had the whole car adjusted within about 2 minutes.
I think it is a nice kit, but I thought it was expensive until I heard mention of an Impreza owner spending about £4k on suspension!