I had Eibach pro spring kit fitted together with a geo, no issues at all, but I have always been careful with the speed bumps. It does lowers the car by 20mm overall and makes the car looks better, especially on the front, ride no harder than before but also no improvement on the handling.
My experience with a 2.2 JTS Spider is different. I fitted Eibach springs over the standard dampers. The springs lowered the car by 20mm, as expected, and it looks better. However, the ride is significantly more firm and the handling is definitely improved.
The Spider is really a Beach Cruiser, as opposed to a sports car, and it's pretty heavy feeling and loosey-goosey in the corners. Lowering the car and raising the spring rate helps produce a more secure feeling car, and not by just a little bit. I would say the change was greater than I expected. Perhaps our perception is different or perhaps the Spider is fundamentally different from the Brera. In any case, I would highly recommend the Eibach springs for Spider owners just for the handling improvement alone; the improved "look" is a bonus.
Speed bumps problems are a function of both speed and height. The Eibach springs don't make things worse under normal circumstances because the lower ride height is offset by the higher spring rate so the car is less prone to bottom out; i.e. medium sized speed bumps taken at medium speed are roughly the same before and after.
Of course, really tall speed bumps that you might find at the entrance of a grocery store, for example, are the kind that you would creep over at 1 mph or less in any case. Naturally, the lower ride height with the Eibach springs will make these more challenging. Still, I have yet to scrape my Spider. Full disclosure: I live in Italy.