Unreasonably flawed.
Great music, but incessantly loud. More distracting than subtle.
Bates was a study of innocence. Perkins performed the role brilliantly, but the character was 'creepy' enough to have caused most viewers to refuse to check in to that hotel. Hence, the scene renders unlikely the chance that Janet Leigh's character would, no matter how tired and regardless of her preceding experience with law enforcement. Hint: study Law and Order's villains. You sometimes can't tell until the very end.
HIPPA notwithstanding, the Psychiatrist's summation at the end should have been Sub rosa/need to know. Too many people standing around listening.
Other flaws, too numerous to name. Easily corrected, if Hitchcock had taken the time or even cared to do so. There is a limit to "willful suspension of disbelief."