Some folks at work use it. Supposedly, the network coverage is good because it uses more than one carrier and picks among the ones the best one to use. The caveat is that you need to use a phone that has modem that all the carriers use.. Most of the phones on the markets are split so that they have radios for verizon+sprint or ATT/tmobile, but not both.
So you would need to get a phone like a Nexus5x or Nexus6,6p that has a modem for all the carriers.
The plan is $20/month for unlimited voice text, and $10/month for each 1GB of data you use, pro-rated based on your actual usage. No data usage, no data charge.
The cheapest phone would be about $199, which if you opted to, you can get it for $9/month.
No flip phone option.
In san diego, coverage would be covered by 3 leading carriers + WIFI.
(I believe that would be Tmobile, verizon, and ATT)
The advantage i think is those that complain about spotty coverage by one carrier in the past haven’t had issues, since supposedly project fi choses the best of the 3 networks each time.
I have t-mobile, and the plan is cheaper because I have a corporate discount and my employer pays for it, and I need to be able to have service that allows me to use different types of phones, so project fi wouldn’t work with me. But, if I didn’t have that requirement, I would probably use it, because at $20/month it’s pretty cheap, and reliability should be as good if not better than each individual carrier. My experience with t-mobile is that the coverage is not that great. It’s tolerable for me, but for example, when I stepped right out side of the SFO airport, I had no reception so couldn’t get an uber cab…lol.