Yes, I've read though all the brake squeal threads but each one seems to have a different behaviour different than mine (on light braking, after stoping, etc, etc).

I'm just finishing run-in on my CS and only did a handfull of harder stops. When driving in a more spirited way on some mountain passes I notice that the brakes sometime squeal for a while just after I come from a heavy/hard braking corner. . I also noticed a "rumble" noise if I make a 2 or 3 harder stops in a row. It stays for a while than goes away when brakes cool (I just hit the brakes harder 2 or 3 corners and they take it easy for a while).

Any similar experiences?

The growling is just the ABS, if it occurs only while your pressing the break pedal during a hard stop. You'll feel the pedal vibrate a hair too.

My '04 M3 did that after track sessions, and I was told that was normal. Since you are on mountain passes, that makes sense too.

might be just some brake pad glazed to the rotor. Just got too hot and stuck to the iron rotor. Thats one of the reasons a cool down lap is so important on the track. To cool the brakes and prevent this from happpening after you stop and park. I never heard of this unless you come to a complete stop though. just a thought.