So far I'm very happy with these springs.
I got these and some Koni Strt struts and replaced my oem struts and springs at the same time. I can't say which component is making the biggest difference, but my ride is extremely smooth and cornering is vastly improved. I feel way more in control of the vehicle. So far (1 week ~ 150 miles) I've seen a 3.5cm (1.4in) drop in the front and 3 cm drop in the back. If you want an improvement over OEM performance for cheap and don't want to lower your car 2-2.5 inches these are for you.
I'm not sure what the Tein engineers had in mind when they 'designed' these springs. True, they did lower my car but the ride quality now is far from 'stock.'The springs do not have enough travel to soak up uneven roads, constantly bottoming out. I could have saved a lot of money by having someone heat up the stock springs with a torch, at least the ride quality would be still be there. I'm very disappointed.