Actually there is a Tape Op magazine article out this month where the mod to an SM57 requires you to soak the shaft in boiling water to get the transformer out. Supposed to improve the low end.
My 57 is from 1980, I won't be doing this mod anytime soon.
I use a 57 all the time for vocals in the studio (especially useful if you don't have a vocal booth)... Paired with a Neve preamp, I am able to get great results... Paired with a crappy pre and you'll get crappy results....