For 64Gb card you have to "manage" it outside of the J3, in a card reader, but after that you can read it and us it without problem in the J3.
Never write on the 64Gb when inside the J3, you will corrupt it, there are no supported a 100%, at less with my San Disk, I know is strange because the T51 (S:flo2) supported it at 100%
About the shuffle mode I agree with you, with the S:flo2 you finally listen always the same songs ^^
The J3 is a nice sounding device when you start using BBE and equalizer, in opposition to the S:flo2 where you enjoy it without effects.
Never write on the 64Gb when inside the J3, you will corrupt it, there are no supported a 100%, at less with my San Disk, I know is strange because the T51 (S:flo2) supported it at 100%
About the shuffle mode I agree with you, with the S:flo2 you finally listen always the same songs ^^
The J3 is a nice sounding device when you start using BBE and equalizer, in opposition to the S:flo2 where you enjoy it without effects.