Charles, is this all the time, or only in certain conditions?
My S65 with the same brakes (I believe) has a pause when the roads are really wet, I think it's a "feature" of the composite discs. Outside of heavy rain/soaking wet roads they brakes are amazing.
If you are getting this all the time, you definitely have a problem as our cars should weigh close to the same amount and the braking performance should be similar.