Update: It has been about a month now and around 90% of people are using GoogleLogin over normal email.
I read the below post about how @tommyjepsen added Google Login and saw a big bump.
For my travel planning app PlanMoreTrips.com, I was offering sign on via a magic email, so no passwords. I thought that was pretty simple login but after reading the other post, it convinced me to push people to login with Google first and then if they didn't have Google, they could login with email.
I added it a few days ago and now all new signups are via google, none via email link.
I don't know how many people in the past came to the site but didn't sign up because adding their email was too much work but now the results speak for themselves.
Anyone that has a site with a login component, I would recommend at a minimum add Google login to your site. I think it will 100% boost conversion and sign ups.
If you want to see how it works, you can see it in action here https://app.planmoretrips.com