I was very impressed with Nick's recordings using these mics with a stock R-4 on archive.org, and purchased a pair from Audiolot a couple of months ago. No frequency plots were supplied with them, but my perception is that they have a pretty extreme high frequency emphasis that goes beyond having a "bright character". IMO they are not very suitable for recording female vocalists. All four attempts I've made using 2 different preamp/ADCs (Core MIC2496 and Oade TMOD R-4) have resulted in an unpleasantly harsh and tinny timbre in the vocals that I've been unable to fully correct for with EQ in post. [You can hear an example if you're interested at
http://www.archive.org/details/cj2007-01-20.aud.flac16 . That edge in Margo Timmins' voice was not part of the venue's mix.] On the positive side, these mics do a great job bringing out the HF transients on cymbals and guitar, and the cardioid caps also feature very clean and powerful bass response.
I think these mics are probably terrific for most instrumental miking applications, and also do a pretty good job with male vocals in my limited experience to date. I'm not a big jam band follower myself, but I would think they're a good choice for recording those types of artists if there are no female singers in the lineup.