Four stars for the app itself, 0 stars for the bugs in OS4 = 2 stars. I have used this app for more than a year, and it is very easy to use and beats paper & pen charting. Some caveats: I am a rapid cycler, so although my luteal phase is 14 days, I ovulate at about day 10 each month, which means the Forecast is always wrong and we cant use it. You can set the average luteal phase in the preferences, but you should be able to set your own average fertile phase to make the forecast more accurate. My husband struggles with interpreting temps and Ws and Ss, so he could really use the ability to set an average ovulation day so all he has to look at is the Forecast. A number wheel to choose temp & weight would be much easier than the keyboard, and I absolutely second the request another reviewer made to be able to sync this app with another iphone. I am sure my husband would really appreciate that one. OS4 BUGS: It crashes in OS4 when you try to access Lists or export your data. It will still be running in the multi-tasking bar, but the app closes every time you tap Lists or export to email. Fix the crash, and its a four-star app. Update to the above requests and Id give it six!