The only reliable hygro I have: The el cheapo from Pet Smart designed for reptile cases. According to the Boveda (sp?), it's spot on. And measured against 2 lbs of Heartfelt beads, it's right at 65%. I was so impressed, I got three more (only one of them was -1% and another was DOA, which I returned).
The adjustable hygros I got from CI: worse than worthless. Initial calibration showed them (I got 3) to be +/- 12%. After adjustment, they were +/- 4%. After putting them into my humidor, they are between them +/- 6% (yeah, their range went higher when I went from 75% humidity of the Boveda to 65% of my humidor).
I've been using those as paper weights.