I've never used IronCAD, so I can't really answer your question, but I've got an opinion. I came to SolidWorks after using two very different CAD programs, Co|Create and Pro/E. SolidWorks had some similarities to each of them and many differences. Sometimes the similarities made it easier to pick up SolidWorks. Sometimes they made it harder, as I thought that they were more similar than they really were and would get tripped up by the differences. The differences can also drive you nuts, because you are used to doing it a certain way and doing it some other way just feels wrong. Overall, I think it is easier for someone with a solid modeling background to pick up another solid modeler than it is for someone coming in without any solid modeling experience.