I've just buyed sandisk ultra 64gb UHS-1 too and have no problem with it. And don't have any problem with exFAT. I'm on CM11, first I do reformated my card on my laptop via "SDformater" (prog for SD hc/hx cards and automatically formats card with exFAT) then put to Gpad and thats it... o and after formating on my laptop I've puted BR movie with 5.1 dts (7GB) for some stres test and works on LG with mxplayer like a charm with 100% smooth (so its prove high performance of tablet too)... I've recomended that card with 100%

***Lil update: I've tested 24gb bluray movie with DTS on Gpad via mxplayer and works smooth, without any insue