As a long term trainer and checker on jets and turboprops I have to agree with Compressor Stall and Leadsled. Learning to fly a new aircraft is not an issue it is learning the task that takes time.
Wether you are an airline pilot going back to charter or vice a versa the type rating is not the hard bit.
In Australia we have lots of hangups about moving up to twins then turbine and onto jets; elsewhere in the world they just get on with it.
Having flown NTAMS in a bygone era I applaud the RFDS for moving into jet operations.
ps I think the last proper aircraft the GAF built was the Mirage!