No bottoming out at all - and I live in New England where the roads SUCK this time of year. Of course I am VERY careful not to hit pot holes and such. Speed bumps are no problem. I like the springs - actually wish they were a bit stiffer as there is still body roll, but I think good sway bars will fix that problem. The ride is very much like stock when just cruising around. The springs become noticable when really pushing the car around corners. I am still getting used to them and the car in general. My 1989 325i still handles better...but it has Bilstein sport shocks, H&R springs, Suspension Techniques sways, Ireland Enginerring strut bars and Falken RT 615 sticky tires on it.....plud RWD and perfect 50/50 front to back and side to side weight distribution. The WRX is a totally different animal. I bet it has better mechanial grip out of the box, but drives totally different.
On a side note - I see H&R just released their springs for the 08 WRX. These were not available and didn't have a release date when I bought the Cobb springs. I have a soft spot for H&Rs. I would like to drive a similair set up WRX with the Cobb and the H&Rs on them to compare and contrast the handling characteristics.
I am totally happy with the Cobb springs and all of their products for that matter.