My husband and I are also in the process of getting our 457. As others have posted we only needed chest xrays and our toddler needed just a medical exam. We were hoping to be there already, but the processing of the visa is taking quite a while. To give you an idea how long it is taking, at least for us, we applied at the end of October. I think the times vary depending on which location is processing the visa application.

Good luck with your move!