I have transfered from pc to mac and mac to pc.Going onto a mac from pc,adding the br3 extension is a good idea.It is a must going from mac to pc. Objects and terrains import well but textures are another story.The texures come out close but not the same.I have found that the best bet is to keep track of textures used and apply them again.If you have edited textures,keep track of how you edited so you reedit. If there is an easier way,I would like to know too.