After ten months of use I can absolutely revise these concerns. Both the measurements and the often-criticized shaking to get under 36 degrees, so far posed no problem.
The only, but predictable criterion, which were not last forever leaves: it is made of glass and careless use also fragile. As well, because it peppy slid with me at clearing away from his hand and divided by the hard acquaintance with the wall. Where other meeting with the floor or cabinet were unscathed.
And the financial aspect: It is comparatively much cheaper than every month or similar to the same or higher price, pills, ovulation tests to buy. Apart from the fact that it is a drug-free, completely natural contraceptive what always impressed me with his accuracy.
So enough reasons to me one more time to order and recommending this course to anyone.