The first service is at 1000kms, which is 620 miles. The service light starts flashing at 621 miles and then stays on permanently from 670 miles. I know, I experienced it over the Easter weekend.
I have a 2005 999, and to confirm what KeefyB said, it states the following:
6000rpm for 1st 1000 kms (620 miles) 7000rpm from 1000kms to 2500kms (1550 miles) run in at 2500 kms.
Can't wait to start opening mine up...the fun only seems to be starting when I have to change up at the minute.