Is anyone using inline RF filters?

YES !!! I still use them on all sorts of equipment. And on most of the non audio stuff in my apartment. Lamps, fans, the refrigerator, all have ferrite clamps stuck onthe cords.
Even though i have two great power conditioners, I still have the ferrite RFI blockers on all the CD changers zipcord AC lines.
I bought a pile of one inch ferrite tubes and slide the cord into then flip it around so the cord runs down inside and back up the outside, then tape it up with teflon plumbers tape.
All my IEC cords are Pangea, and too thick to add any ferrite, though the Pangea work fine without any such device on them.

Hi Elizabeth - Do ferrite chokes (which I use) have the same functional effect as an in-line filter as the one I am linking to?

http://www.arraysolutions.com/Products/nqnaclinefilter.htm

That device is a powerline conditioner. Far more than a simple ferrite on the cord.
It has caps and other device inthe line.
I have no idea what that device would do to an audio signal the cord is connected to.