I have a closely matched set of 57's from years ago. I hang onto them as I will get a call that specifies a 57 on a guitar amp... I occaisionally take on a sound job... I would vastly prefer an I5 or a Senn e-609 on a guitar cab but sometimes a 57 is what is asked for...
More and more folks are getting hip to the OM-7 as a vocal mic. Not cheap but it is near in a league of it's own as far as transparency, dynamic range and feed back rejection. Fabulous mic! I stopped singing on my 421 due to the Om-7...
609's are great, presence peak at 4k as opposed the the 2.5k peak on the 57 so, it's really about where you need the sound to sit in the mix.
OM-7 is great if the singer sings loudly, directly into the mic
at the same distance without variation... an important aspect to know about this mic because it definitely won't work for everyone.
If buying an om7, i'd try the "r" version (dave rat version) as these are supposed to be more consistent sounding from mic to mic due to a couple minor design preferences.
Another thing to keep in mind is the om7 requires a lot more input gain than most mics.
Transparency is actually an issue I had with audix as an endorser. I was given a whole compliment of their mics for foh touring work, but found them so clean in the low mid and bottom transients that i'd be pushing amps hard before realizing it, and getting frequency buildup that was only apparent when multiple mics were open. I still use a bunch of their mics, and the d6 is a perfect example of this extreme cleanliness- if I need a mic for ultra attack/ metal kick drum sounds, this is my go to.
I currently have a sennheiser deal, but it's not exclusive as I prefer other vocal mics- it's really for the drum mics and wireless iem systems. My current clients are using telefunken m80's, which have been great- they do have an extended top end like a condenser which can be problematic in close quarters, but otherwise deliver a very detailed sound.
The one company which I love, and have not been disappointed in a single mic yet, is beyerdynamic. But they are rather expensive, at least in the states.
The beyer m201 is the 57 and 609 killer imho.