Well, I hate to confirm the naysayers, but this addon Just Doesn't Work™. I have pass installed and working just fine, I followed the installation instructions to the letter, but the script to install the host app appears to do nothing and the "Troubleshooting" section of the instructions doesn't list the error the addon is giving me ("Connection to the host app failed or returned an unexpected result! Make sure you have the latest version of the PassFF host app installed by following the official installation instructions." - which is exactly what I did, and I'm still getting the error.)

It's been a pleasant couple of hours thinking that this would actually work with my copy of firefox, but I'm uninstalling and getting on with my life now.