BTW, it doesn't make much sense for Google to sell this information anyway. They build vertical products on top of this information. If a third party wants identity verification, they can use Google account. If they want to sell ads, they can use Google ads. By providing information directly, they will be undercutting themselves. It doesn't make sense.

Yes. It's basically an MVNO that resells on Sprint, TMO, and US Cellular, while trying hard to keep calls and data going over WiFi. As a consequence of that, it only works on newer phones that can do fast handoff between WiFi and cell. I use it. It works pretty well. My wife is still on Cricket and she got better coverage in the mountains of Colorado this summer, but I've been happy everywhere else.

The pricing is very as-you-use it, which works well for some people and not as well for others (it's great for people who use very little data but want flexibility; the international data roaming is amazing; it's more expensive than other plans for multiple-GB/month users). I put together a spreadsheet (copyable, google sheets) for comparing price vs GB/data used when I was trying to figure which carrier to use. If it's useful - https://da-data.blogspot.com/2015/10/comparing-prepaid-cell-... (Updated: I just updated the pricing, since it was getting a little stale.)

(Ob disclaimer: I'm part time at Google, but have no beans in the cellular stuff.)

Under the hood it uses Sprint and T-Mobile's cell networks, so you're not completely free of them. But otherwise, yes it's a great replacement and the billing/plan is much better than the regular carriers.

Absolutely. It uses T-Mobile's network most of the time and T-Mobile has improved a lot in the past few years. Sprint and US Cellular are good fallbacks for rural areas.

Another perk is unlimited international data roaming at the same price as regular data, and at decent speeds too.

Billing is simple, support is great. The one downside is data is a bit on the expensive side. But since you actually pay per GB, the GBs are yours. There are no arbitrary limits or throttling that I'm aware of, tethering is allowed, etc. Also you don't have to predict your usage ahead of time to choose a plan. You only pay for what you use no matter how much or how little.

Disclaimer: I work for Google (but not on Fi)