I am on Google-Fi. Performance / coverage is pretty good, but I can't compare to ATT.

I will say I feel like the pricing isn't very competitive with other carriers, as it was ~2 years ago. Fi is a great choice for someone who knows they will be on WiFi the majority of the time, and want to keep your wireless bill <50$ a month. Once you start using data, it gets pretty expensive, even with their recent data cap protection.