Built Right sexed semen never worked for us, and according to some other people on SP, it wasn't an isolated situation. After using 13 straws, we had 18 unfertilized/0 fertilized eggs on a flush (used 6 straws), and 1 for 5 on AI use (some we used 2 straws on), we got 1 bull calf and no heifers! We haven't used all the Simmi bulls that have sexed semen available, but from experience I can tell you that In Dew Time does work. Only caution I'd give you on these young bulls mentioned is that it's a big chance to used the sexed semen until you know what success rate people are having. So many bulls don't have the fertility level needed to successfully sort the semen and still be good enough when thawed.
For what it's worth, I have one unit of B.R. sexed semen left that I'll gladly give away!
Just my $.02!