I just got my Space Star back with the Eibach Pro-Kit lowering springs yesterday. Comfort is quite good, no big difference to the standard springs. There is only a bigger difference when driving over deep pot holes or road humps, but the body is stiff enough that there are no additionally noises even on cobblestones. The front springs have a linear spring characteristic curve, the rear springs are progressive.
In my opinion, the Eibach springs work much better than the original springs. Comfort is really good compared to other cars (like Audi A1 or Toyota Yaris) but not excessive soft anymore. Body roll and pitch are reduced and therefore driving round corners is much more fun. The boot contents and the passengers don´t slide around at low speeds anymore because of the lateral inclination even at low speeds.
The car looks really good now, the distance between the tires and the fenders is now steady and the car looks more sporty, consistent with the tinted windows, the alloy wheels, the big rear spoiler and the front lights.
Until now I can really recommend the Eibach springs but I will write down more experiences in the next weeks, especially regarding fuel consumption and handling. I did not make any pictures of the whole car until now because it is very dirty and the springs maybe will lower in the next weeks, too.
PS: It would be nice to add this thread to the "Suspension & brake aftermarket parts index" sticky thread.