Those of us who have edited screenplays for friends, for acquaintances, for business contacts and for money recognized every.single.line.
What I usually do? I write out my line-by-line gripes and if they're useful, I include them. If they're harsh enough that I think they might crush the person on the receiving end, I don't. Either way, I give them a nice 1500-2000 word summary of the strengths and weaknesses.
But if you're trying to whip a manuscript into shape, the line-by-line shit is all that matters.