I used them mixing in ear monitors for maybe 60 shows on vocals. Now I'm mixing FOH using them on snare, under snare and bells/crotales. My current lead vocalist tried one in rehearsal with IEMs, but preferred his OM7 (maybe for isolation? I wasn't there to witness or adjust).
Audio quality and side/rear rejection is excellent. I still pick up high frequencies if the mic is pointed at cymbals (I try to angle vocal mics away from high hats), but otherwise great gain before feedback and isolation. Less EQ is needed in general compared to a 58...less low end proximity effect, dips in response around 400 hz and maybe 2.5k, but a bright presence from 4k to 8k (like what I often do with EQ to a 58). Less distortion than a 58, my impression is it sounds more "hifi-ish" but still has great gain before feedback. Regarding the earlier question about which voices wouldn't sound good with this mic, I'm guessing voices that have peaks at 4-6k, heavy sibilance issues, or a lack of low mids around 400hz.
Clip is terrible (can't hold the mic up, hard to tighten, prone to tearing apart when tape inserted to tighten, prone to brass threaded part coming out when mic stand slams the stage), BUT Telefunken is designing a new better/stronger one that is "nearly ready." The Audix vocal mic clip works great with them. The Shure clips are a bit stressed to receive the large shaft, though I'm still currently using them on snares due to neccessity.
When thrown to the stage repeatedly, grill is more likely to come apart than a Audio Technica AE6100 or SM58. Depending on the severity, usually about 4 hard "drops" will pop open the grill around the ring. Telefunken has been supportive with spare parts.
When thrown repeatedly and grills are repeatedly damaged and replaced, audio degradation was only noticed after MANY drops. I've been told this is likely transformer/connections damaged. Result was a loss of gain, maybe 10 db and slightly different tonality. This happened with 2 mics out of around 60 shows averaging maybe 5 hard "drops" per show.
I am now currently using them on snare tops and bottoms, for a much more "hifi-ish" beefy sound and more isolation than a 57. Also using them on bells and crotales, with same results.
Telefunken can make very pretty gold and silver ones. See ZZTop for silver, AFI for gold.
I did not notice much handling noise with an agressive singer and a vocal heavy in ear monitor mix, even in the shiny metallic model (rather than rubber finish). I never muted the mic in the monitors despite lots of "drops" and replacing the mic in the clip.
Telefunken seems eager to work with engineers to get the mics out there.
Definitely worth a try. I've watched engineers get VERY happy when trying these as a lead vocal mic. It's hard to beat a mic that sounds hifi-ish AND has great gain before feedback.
Denny