i've got a b1, and i bought it due to the overwhelming "thumbs up" nature of most of the threads here.
djl seems to be a nice enough guy and gives pretty good recommendations, but he seems to have a bone to pick with either alan or studio projects. whatever--that's his perrogative, not mine, and i'm staying out of it. even so, even djl recommends the B1 for some tasks. the proof is in the pudding--it's a solid mic, especially at that $80 price-point.
i've used it on several vocalists of various levels of "professionalism", myself included. for some vocalists, it sounded quite pleasing. for some (myself included) it pretty much "sucked" in that it emphasized everything about my voice that i did NOT want emphasized. in that regard, as is the case with everything else, YMMV. now that i've got an re38 (which sounds great on my voice, btw), i don't think that the B1 will be my "main" vocal mic anymore, but given that that was all i had (other than the sm57/8/senn835 type mics), the B1 did an admirable (read: extremely usable) job on some vocalists and i still plan to set it up alongside the re38 when doing a mic test for a new vocalist (or for a new song), b/c ya never know.....
however, the strength of the B1 lies in the fact that it's good at so much more than vocals. great on acoustic guitar and fantastic electric guitar amps (in my experience, especially on low wattage tube amps), some love it as an overhead or room mic, and i love it as both a snare and hihat mic. couple that with its "sometimes usable" quality as a main vocal mic, and you've got a pretty good deal for $80.
by all accounts, the mxl v67 is a more "colored" or "hyped" mic than the B1, and therefore more "traditionally tailored" for use as a main vocal mic, but by most accounts, it's also not as versatile as the B1. again, YMMV. i've not used a v67, and i really, really comtemplated getting one for a long time until i got the RE38. now i think i'm gonna actually go with
a v69 instead (after a couple other nice dynamic mic acquisitions--see below).
for a long time, the C1 was VERY popular around here. lately, though, it's suffering from the "morning after effect" and some folks don't think it's as great as it was initially hyped and thought. again, not ever having used one, i would suspect that the truth lies somewhere in the middle. however, given the $200-ish price tag, i would rather save another $50-100 and buy a nicely used dynamic instead--an RE20, or maybe an sm7 or senn 441. any of those are pretty much "proven winners" in the main vocal mic category.
but back to the question at hand, the B1 is a very versatile mic, especially so at the $80 price level--and as is the case with almost every mic, happens to be "quite usable" on some vocalists, while "not as pleasing" on other vocalists.
in essence, i view the B1 as a medium-diaphragm condensor version of an sm57 (at least in terms of variety of usefulness and bang for the buck).
wade