My brother does this. Personally I've never had trouble waking up...if anything my problem is falling asleep and staying asleep all night. I tend to stay on an early-to-bed, early-to-rise schedule, which is convenient for work and class but inconvenient for social life...overall I think I prefer it to constantly having to fight my internal clock. My main problem is mid-afternoon sleepiness on the days when I don't quite make my 8 or 9 hours.