Turns out the packages from the official repositories do the trick. Just install
exfat-fuse packages using the package manager of your choice, or just using
apt-get from the command line:
sudo apt-get install exfat-utils exfat-fuse
This should delivery a working exfat file system (read and write support, but not formatting the drives with exfat via Gnome Disks and GParted).
From 13.04+ it hasn't been necessary but if you're using 12.04 you might need to reboot your computer before you can mount your exfat partition. If it isn't working for you after installing the packages, try rebooting.