When I have finished with the authoring, have run a simulation and am happy with the results I go to the Burn drop-down menu and choose "Write Disc Image..."
before I had a Blu-Ray burner I used to choose "Write Volume..." and then copy the M2TS file that was created in the process onto a Memory-stick or a DVD - then play that file on the PlayStation3.
A menu will appear where you can choose "DVD" or "Blu-Ray"

After a long wait for the transcoding I should find the ISO file in the directory I chose for the DVDit project.
It is then a simple task to burn the image to a Blu-ay disc (see from page 14)
But first let me explain why I deselected the "delete temp files earlier"