Pros: Easy to use, compact
Cons: Lightbulb wore out quickly
I bought the Ovulens around the time that my son was born, because my husband and I wanted to use the Fertility Awareness Method. The book, Taking Charge of Your Fertility, is really helpful if you would like to know more about how your body and your cycle work. The author recommend using a thermometer to help chart your fertility, and warns against using only an ovulation detector (which seem to be designed for achieving rather than avoiding pregnancy). However, I have had good results so far using the Ovulens and observing my cervical fluid. The Ovulens comes with good instructions, and is pretty easy to use. They recommend taking one drop of saliva(without bubbles in it)before you eat or drink anything in the morning and placing it on the small magnifying glass, waiting till it dries and then looking at it with the light that is part of the instrument. You then look for any ferning patterns, which indicate that you may be fertile.
The only complaint I have is that the light started flickering not too long after I purchased it, and there doesn't seem to be a way to replace the bulb without damaging the product.