I purchased one of these 64gig cards, and YES they do work, but sometimes you have to rescan your media for new files to show.
Also, I had to format fat32 (do not use quick format, won't work) on my PC before
phone would use it correctly. Format takes 15 minutes or more.
If you format it on the phone, files can become invisible on mass media and myfiles app.
In settings/storage shows full 59.46GB
Mass Storage on PC shows full 59.46GB.
I have been using it for a week now, and only problem is sometimes files will not show up for a few minutes. They are there but I guess it takes time for the phone to rescan.