Dating scans seem to be all the rage at the moment. But, if you know your dates, then you don't need to have the early scan. It's a good scan to have if you really have no idea of how far along you are, but if you have been trying to conceive and know when your periods have been or ovulation, then they are far superior dates to go off.
The jury is still out on the safety of ultrasound so I think it's wise to use that technology with a degree of caution. It can also add to the medicalisation of pregnancy particularly if you are receiving care from an Ob.