Update July 13, 2020:
It's working again like before ☺👍

Update December 11, 2019:
Since the latest Firefox update, this addon doesn't work any longer for me. I don't like to give it 1 star rating but I tried troubleshooting myself. I gave it access to private browsing, reinstalled and also tried on a new Firefox profile. It simply won't work.

I like that it has a kill switch and offers many regions, including some handy privacy protection features. Along with Firefox's container tabs, it's a solid tool against trackers. It's not free from bugs but I notice that simply uninstalling the extension, restarting Firefox and reinstalling it fixed all my problems I've had with it so far. My last problem was missing regions but a reinstallation fixed it.

I have been using PIA, pretty much since inception, which I learned about from the great Anons on 4 chan. Banking, shopping etc. are no longer a paranoia inducing experience. No sweat, no stress, just easy to setup and utilize. The web is not a scary place thanks to Private Internet Access!

generally okay xcept bbc and nflix are onto it ...

The privacy access for this add-on is atrocious. Check under Permissions, and you will see:

-- Access your data for all websites
-- Download files and read and modify the browser’s download history
-- Access browser tabs

How is this OK? I understand their need to protect against phishing, etc, but access to ALL data, that's borderline unethical and vast potential for data leakage, and corporate maleficence.

Some additional quirks, as noted by others. Sites such as nextdoor.com will not allow login, even when PIA is not connected. The extension needs to be disabled.

One cannot connect if zscaler is running on the OS.

My router firewall was somehow blocking the extension from finding and connecting even though Firefox itself was working fine with router firewall active. I disabled router firewall and PIA extension connected fine. I then closed Firefox and activated router firewall. After that the Firefox and PIA worked perfectly except PIA won't allow changing location unless I repeat the process of disabling-enabling router firewall. If I use the PIA Windows application this issue is not present.
Edit: The issue also occurs with Google's Chrome browser.

So far, so good. I will update my review if I run into major issues. I think people experiencing issues in private browser windows do not have the option for it enabled on the extension. I am running the extension, and the desktop app at the same time. I have also tried it with the desktop PIA app turned off, and have found no difference.

Web Developer Google Marketing Global Partner

Very good vpn extension for Firefox. Occasionally I have long ping times, but overall I recommend PIA

On latest update, as soon as I open any private window it logs me off completely, I have to relogin to my paid pia user account to continue using it. Without private tabs it seems reliable enough, but any one single private tab - and it logs off. I've been paid user for more then a year now, but now I consider switching, since reliable vpn is required for my work.

Satisfaction Beyond Description...

Superb app. I love it!