I ended up switching to Mobile-X since I'm on wifi so much I only use a few gigs of data a month. $2/month + $1.90/GB vs Google Fi's flexible plan of $20/month + $10/GB.
If you travel internationally, they're really cheap relative to everyone else who will charge you absolutely ridiculous roaming fees.
The Google Fi plans with roaming are either $65/month (100GB) or $20/month + $10/GB. I often end up using quite a bit of data abroad.
Having moved here from the UK where I was used to cheap mobile plans I just grate at how extortionate they are in the US.
The single place I noticed verizon gets coverage and tmobile doesn't is three levels underground in a concrete parking garage.