My OBGYN told me that it's just a computer and our bodies are not computers, so when it says you've ovulated, you can't really be sure (although, obviously a temp jump shows ovulation, so not sure why she said that, but I guess how FF changes crosshairs sometimes, it's just an estimate).
Then I went to the FS, and he said the same thing, basically. If you click on my charts (there are plenty of them on there), there is usually a jump, but then it jumps back down. The specialist said 'You don't look like you have ovulation problems to me. That software is outdated, and it's just a fun exercise. If it makes you happy to do it, keep doing it.'
From those two statements, I kind of take it with a grain of salt, but since I'm an old gal, I kind of believe FF and sometimes I ovulate and sometimes I don't. I'm waiting for AF, and then I go back to the FS for the next steps, so we'll see what he says this time. My crosshairs got taken away with my low temperature this morning, so I'm feeling a bit frustrated today. All that BD time for nothing (except fun)...once again.
Edit-And I will say, that it is good to have data when seeing a doctor so you can show them what you think is happening, but they think they know all the answers and you don't, so I think they'll probably tell you the same thing when the time comes...let me know..ha!