No I haven't used it. I am planning on using an R53Hn (AR9220) myself.
Wireless support on pfSense basically boiles down to support on FreeBSD. Over there support for our cards is still being worked on. So don't expect that it works out of the box with pfSense.
Adrian seems to be the main developer busy with the Atheros support, so keep an eye on his work:
It says your device works in latest head. So it isn't integrated in the pfSense kernel. You have to build your own module.
Same for me. I am going to build the svn current kernel (head) on a separate machine using VMware and see if I can copy and load the modules on pfSense.
Thank your for the info. Just the kind of info I needed. For the sake of simplicity I'll purchase a a/b/g card for the time being.