Most MSPE's are a standardized description of your performance in medical school. It's not a recommendation per se, as the "dean" (or whomever writes the letter -- there's usually a committee) probably didn't work with you directly. But it's still one of the most important documents in your application, as it (usually) clearly defines how you did compared with others at your school.
MSPE's are standardized within a medical school to a certain extent, but obviously as APD has pointed out, some schools edit for content and some school just paste and copy from clerkship evaluations. The begs to question how standardized the MSPE is between medical schools.
I would disagree that the MSPE is the one of the most important documents per se (at least for lower to middle tier IM, Peds, Family . . . ) as when I applied for residency I got a ton of interviews, most before November 1st, before when the MSPE is supposed to be released.
I surmise that if you have a good to excellent grades the MSPE would add little to your transcript. If anything considering how sloppy clerkship evals are, i.e. vague comments that students and deans have trouble deciphering, how much help could such comments be on an MSPE? Anyway, my MSPE was spotless, so some schools would rather NOT slam their students, which may or may not be fair to others and might make your MSPE worthless, but at least it is not a strike against you.
I would argue that the most important document would be your USMLE transcripts, i.e. step scores as if you can do well on these this gives you a leg up on getting interviews and all the way through the process. Followed by your medical school transcripts, and then perhaps LORs specific to your field.
Maybe APD runs a top-tier IM program where maybe they would look at MSPE's to help distinguish between excellent and super excellent applicants though . . .
