I've used an ultrasound for the past few years to assist in my breeding. It is my opinion that an ultrasound machine is very informative, but doesn't really make your breeding more successful. If you really want to know to know how many eggs your girl will have, wait till their laid and then count them!

The one area I think that an ultrasound can really change breeding results is when you are trying to maximize a male to an un-godly number of females. That's just not something I've ever really tied to do.

Justin