I've now been using this system for over 5 years... with no conceptions.
It's a great solution if, like me, you cannot use other methods such as The Pill.
It is totally natural and makes you far more aware of your cycle.
I agree with everything the previous reviewer has said but would also add;
- stick with it for at least 6 months while the device 'learns' your cycle. You get a lot of 'red days' when you first start using it and it feels a bit frustrating, but once you've been using it regularly and correctly, the red days come down to about 5 per month.
- if you have very erratic cycles or very short/very long cycles, it may not be for you as it can only cope with a certain level of variation (but it's still a pretty wide tolerance).
- yep, travelling with it can be a pain, especially if you're changing time zones. Tip: Keep a few of those sterile sample bottles (from your GP) so you can collect the first urine of the day but store it for the when you get the 'amber light' which is a specfic 6 hr time window (that you choose). Obviously this course of action is generally only necessary on the odd occasion... before I put you off!
I think this system is marvellous and regularly recommend it (should the topic arise!). It's nicknamed the 'catholic mating machine' in our house! :o)