DFB - yes, some people didn't like it at all...it takes a while to get used to how much saliva to use, and you need to understand the different types of ferning too. I also found doing it twice a day helped, as I'd have no ferning one morning, full ferning in the arvo and just a little the next day. If I hadn't done it in the arvo, I'd have missed it...or still be waiting for O!

Remember some meds can mess with your ferning. I also read that CM does the ferning thing too, but never tried it.
So mant mixed reviews... if it was only $20 I would just buy it, but being so expensive I am not sure I can justify it, well not with DP agreeing anyway - haha.