Just an update on my too-much-resistance problem (which Mitch, primarily, was helping me think through): I've been biding my time, trying to figure out whether I could become happy with this unit -- also trying every kind of technique, grind, etc. Since Firefly had already replaced my first unit, which worked wonderfully but had a strange flickering light, I'd been kind of dreading the proposition of another exchange. But I finally realized I would never be happy with this one, especially since I know the pleasures of well-functioning Firefly. Happily, Patrick at Firefly did not hesitate to offer a quick-turnaround replacement, so, hopefully, the third one will be the charm.
Since people say there are natural variations among units, I'm still not sure if my current one is actually faulty, or just on the extreme edge of the spectrum when it comes to temperature and draw resistance. What I do know is that the only way I've been able to get by with it is to clean it completely every evening, including under the screen -- yet still the draw is too hard, and the taste is sour after the first inhalation. So my guess is that some sort of variance is incorrect -- maybe too much or too little space at the bottom of the bowl. I does strike me as strange that such a precision product made out of hard materials would vary significantly from unit to unit. But I'm looking forward to receiving my replacement in a few days. Maybe Firefly will be collecting data on all the returned units to help them minimize such variations/flaws in their next version.