I've noticed one little quirk after using the 64GB card for a few days --
When I reboot the eDGe after shutting it down fully, it spends a few seconds "checking SD Card for errors". It has yet to tell me it has found anything wrong. I never noticed this with my 16GB card. I dunno if it is shutting down before it can cleanly unmount the card? Any ideas? Otherwise, it is working perfectly. I played some podcasts off it today for about 2 hours with it underclocked/volted to 156mhz and had no problems.