I'm on H&R Race right now on a 330Ci Sport. It is very low, so take that into account as you will have to go at angles for steep driveways and speed bumps will be your enemy. That said, it's not that big a deal for me. I love the super low stance and the ride isn't that bad. With stock shocks it is quite bouncy on uneven roads. That is to be expected when you lower a car without putting matching stiffer shocks to dampen the reduced suspension travel.
H&R Sport may be a little easier on your stock shocks than Race, but the drop isn't as aggressive. Search on www.e46fanatics.com/forums
for more info. This topic has been beaten to death over there.