To add another data point. I just did this mod to my 09 E90 (July 09 Build) w/ 30k miles. My spring assembly had 2 springs in it. I'm basically gonna reiterate what everyone in this thread already said.
Removing the spring assembly did cause the pedal to have extra side-to-side play. But after driving the car w/o the spring, I really like the way the clutch feels. I can live w/ extra side-to-side play in the pedal. That extra play doesn't affect the clutch actuation. I barely notice the extra play while driving.
The clutch pedal effort did increase slightly, but not much (maybe by 10%). It's nice to be able to feel where the engagement point is. I've only driven the car 2 miles since doing this mod, so it might just be my imagination. But my shifts feel smoother!
Overall, I'm really happy with this mod. I feel more connected while driving.
Next mod, illuminated ZHP knob!