We sync all our recips as well. A local Red Angus breeder flew to Alabama a couple years ago and took a week course in implanting embryos. He has been implanting his own embryos and he is thinking his success is due to his implanting on natural heats. He purchased a set of 4 embryos from me, and got 4 calves in 09. These were the first he implanted himself. He purchased 3 more last year and he thinks he has 3 pregnancies out of 3 implanted. He has been implanting some for others, and implanting on natural heats and they seem to be very pleased. This year, if I can talk him into this, I am going to try to compare a set of embryos implanted into a set of synch'd recips, against another set that were implanted using natural heats. Of course the ET vets tell you that there should be no difference.