I've got no trouble getting up at 6-8 am. If left to my own devices, I get up quite a bit later, though. But never mind my actual sleep phase (or whether I sleep 6,8 or 10 hours), it still takes me 30-60 minutes to fall asleep. So becoming a morning person isn't a good fix for everyone.

(and the "3 Guinness" method has its flaws in the long run.)