Does anyone using engine brake? Is it effective on brake distance?
And, what is the 60-0 mile brake distance of imprezas?

Perhaps by helping prevent any individual wheel from locking, but that is taken care off by EBD. I am not sure if it will help stopping distance. Stopping quickly is also about smoothness and engine braking can be quite jerky.

The last skid pan I went on the police said it is accepted in emergencies you de-clutch and hit the brake at the same time. From 60 (I think) that technique has proven to stop the car by a cars length shorter than keeping the clutch engaged. The theory is that the brakes fight the engine in the short time between the engine having power on and power off.