I am a 3rd year in medical school, and firmly believe that sleep deprivation is a terrible weeding process. If a doctor is sleep deprived I do not want them touching me with a ten foot pole. They make enough mistakes as it is! Sure you argue that they limit work hours, but I can tell you first hand that these limits are only paid lip service to, and I routinely see residents work 80+ (sometimes 90+) hours a week. Oh and the max shift is 16 hours now so calculate out how you get to 80+ hours. You can't report your program because they will lose accreditation and you'd have to go somewhere else to get this scam of being 'board certified', and you can't really threaten because your program can find a reason to dispose of you. real big catch-22.

(just for kicks, if you worked 10hour days for 7 days a week that is only 70 hour work week... doctors work at least 12 hour days, and usually 16 hour days to get to the full 80 hours!)

Oh and as far as weeding out?

Most 'weeding' out happens first and second year of medical school. In my class alone about 10% of the class failed first year exams, and they were forced to repeat or retake the whole year. (which SUCKS when you just paid $37,000 for a year of school that meant nothing). Then Second year weeding happens again with STEP1 licensing exam:

"Overall pass rates for first time USMLE Step 1 test takers are: 92% for U.S. M.D. medical school graduates, 81% for U.S. D.O. osteopathic medical school graduates, and 73% for international medical school graduates" http://en.wikipedia.org/wiki/United_States_Medical_Licensing...

Fail a year or a board exams? You pretty much can only be a psychiatrist or family doctor with little or no hope of every specializing.