I recently installed EBC HH pads front and rear - have about 800 miles since then, so they are completely seated.
What I notice -
a) sound - EBC HH squeal when braking - gets better over time but never goes away completely
b) braking power - initial bite is unbelievable, so you have to readjust your braking technique to get that gradual feel back or you will do the unintentionl stoppie easily (don't ask how I know)
c)increased drag - gets better overtime, but never goes away completely
d)my disks did show some darker areas but it doesn't affect braking, its not like they are glazed, but just dark, I have to use some brake cleaner and check it out again