I haven't, and while I doubt that I would have gone for it without university either, after having taken some reproduction classes, I would absolutely never.
Even hormone control can't be totally reliable, so there's no way I would trust my own sense of timing: temperature fluctuations can be for other reasons, and either the sperm or the egg could live longer than anticipated... 80-85% effectiveness isn't good enough for me, and that's betting that I'm one of the few who's consistent enough to pin down her ovulation exactly. Studies out there that have shown higher success rates have also been revealed to have cherry picked the best data (very, very poor scientific methodology), and there's a consistent national average in the US of about 18% failure per year. A one in five chance of a baby? Nooooo thank you.
Not only that, a safe buffer is MINIMUM seven to ten days, because you have to stop both before and after ovulation for effective control. I don't think that I'd like to live two thirds of my life not having sex when there are many, many other options.
No I have not used this form of birth control, and most definetly would not either. I agree that there are far more reliable methods for birth control then The Rhythm Method. Who comes up with this stuff? I like to gamble as much as the next person but creating a life and then raising a child isn't something I'm willing to leave to the odds. Lol. Plus there's no added benefit of protection from STDs.