Although this mic is now considered primarily an instrument mic, that was not always the case and I've actually preferred this same basic design for live vocal use since 1970 when I bought my first one which was then known as a "Shure Model 545 Unidyne III."  That mic got stolen about 2 years ago, but remarkably was still working at the time it got boosted and I was still using it when I needed one with an on/off switch function.  I've owned or used countless modern day SM-58's and SM-57's along with dozens of other mics over the years from all manufacturers.  I have a fairly deep baritone to bass type voice and I don't need to get closer than about 7 or 8 inches to a SM-57.  To me the SM-57 sounds similar to the $469 Shure SM-7 studio vocal mic if you put a windscreen on it and get about 2 inches away.  I'd only use an SM-7 in a studio environment though because they are slightly more fragile and over four times as expensive.  By design the SM-58's require you to get much closer to the mic to get a full range sound than with the SM-57's.  I prefer the SM-57's over the SM-58's for vocal use because they sound crisper on the highs and they sound fuller on the low end.  The SM-57 sounds more natural on vocals and never sounds muddy or muffled.  The SM-57 has one of the most pronounced proximity effects of any mic I've ever used.  If you tend to shove the mic down your throat you may benefit from the less dramatic proximity effect of the SM-58.  If you are ever going to use an SM-57 for vocals I'd recommend buying the Shure A2WS windscreen with it.  That genuine Shure windscreen fits precisely and locks securely onto the SM-57.  The SM-57 will pop like mad without one.  The only possible drawback to the SM57 as a vocal mic is that there is no model available with an on/off switch these days.  I can't find a modern SM-57 with a switch anywhere.  However, if you've ever tried using a mic when you forgot that the switch was in the off position it probably just became a liability. For my money, the SM-57 is the best all around microphone of the past two generations for stage use and some recording purposes.  For studio vocals I'd use an SM-7, which really doesn't sound all that much different from the SM-57 when the built-in variable EQ on the SM-7 is set the way I like.  The SM-57 and it's predecessors are to me the best all around microphone since 1970 and certainly the most enduring and durable.  You can not go wrong unless you get too close with no windscreen.