I don't know. It's always hailed as a monumental breakthrough, some kind of maturing thing, but did the world really need rock and roll bands singing ballads set to strings? I for one hate the fact that the greatest R'n'R band in the world could well be remembered for this granny pleaser, and cue a hundred otherwise good hard rocking bands hitting the charts with totally out of character power ballads.
I think Yesterday is a bit of Pauls Frankenstein, and the monsters gonna get him in the end.