Hi Dennis, I think the may just be a case of who your check-in person is. I have had no issues going PER-IST-ATH in the past, but going back the other way I've had to go to a transfer desk. I'm yet to have been forced to get my bags and check in all again at the transit airport. 

I spoke to Singapore Airlines who confirmed that they would check my bags through all the way to Athens.Worst case scenario, the transfer desk at Istanbul would ensure re-tag the bag and give me a new baggage receipt at the gate 

Very interesting. I have a Singapore Airlines ticket from Perth - Istanbul and an Aegean ticket from Istanbul - Athens. Without the Star Alliance through check-in this would not be possible. I think I'm definitely sticking with Star Alliance after this news. Anyone else feel the same way?

Intersting. Chris, what do you think are the advantages (if any) of the Essential card over the AMEX Platinum Edge card? Which would you recommend?