I have just got my jolla to mount a Kingston 64Gb SDXC card out of the box - which required building exFAT support.

I am running SailfishOS 1.0.4.20

This is what I did

open Web Browser
Go to http://code.google.com/p/exfat/downloads/list
Download both files:
fuse-exfat-1.0.1.tar.gz
exfat-utils-1.0.1.tar.gz

open Terminal
devel-su
pkcon install gcc gcc-c++ scons fuse-devel
cd /home/nemo/Downloads
tar -zxvf fuse-exfat-1.0.1.tar.gz
tar -zxvf exfat-utils-1.0.1.tar.gz
cd fuse-exfat-1.0.1
scons
scons install
cd ../exfat-utils-1.0.1
scons
scons install
REBOOT phone with card inserted
SDCARD mounted as /media/sdcard/0123-4567

In terminal I navigated to the directory and did

touch blob

The file blob was created. I edited blob with vi and saved it, mored it, and also deleted it.

Obviously /media/sdcard/0123-4567 is the default place on my phone and I havent played around with this.

df -kh reports

/dev/mmcblk1p1 59G 17M 59G 1% /media/sdcard/0123-4567

I downloaded using the web browser as I couldnt be bothered to try and sort our subversion on my phone and follow the google code instructions

I dont know if both fuse-exfat and exfat-utils are required, maybe someone else can comment.

The sdcard is not being recognised by default in CargoDock.

I havent done anything else as yet ....... so not sure how well it functions.