I'm really excited about this idea, but I also think it isn't fully baked yet.
I'm excited because VPNs are all about shifting trust: I'm no longer trusting Comcast not to sell my data, I'm now trusting SketchyVPN. If SketchyVPN turns out not to be trustworthy, then I'm paying for something that is worth less than $0 to me, and there's no way to detect that as a user. It's like paying more for organic food in a town where farm stands are paid to lace organic food with arsenic -- why would you?
For VPN service, I trust Mozilla more than to just about anybody: they're nonprofit, have clear and transparent governance, have many mission-driven employees, and would lose more than they could possibly gain by breaking the terms of service on a VPN. They also have a big enough profile that it takes no extra effort to stay up to date on how trustworthy they are -- they do make missteps, but every misstep hits the front page of HN, which is exactly what I want. If they run a VPN, I'm sold that it's worth more than $0.
But the service isn't fully baked yet for me, because they're not explaining how they're enforcing the trustworthiness of ProtonVPN. I have no idea if ProtonVPN is as trustworthy as Mozilla -- maybe it is, but I don't want to learn and stay on top of that. Instead I want premium.firefox.com/vpn/ to convince me that, if I use Mozilla's service, I'm fully benefiting from their trustworthiness.