I'm finally sick of Verizon's shit to the point that I want to switch. They're expensive, nickle and dime you on buying phones, heavily lobbied against Net Neutrality, and refuse to sell a phone without a locked bootloader.
Project Fi is the one that I keep coming back to, but I'm not 100% sold.
Basic plan is $20 for unlimited calls and texts, plus $1 per 100MB of data usage (so $10 per GB). No contract, so you're only charged for what you use, and they cap your bill at $60 for a given month without cutting off data. It also uses 3 networks (Sprint, T-Mobile, and U.S. Cellular), and will jump to whichever tower is strongest at the given moment.
But there are two things that give me pause. The first is that there have been some complaints about phones leaking data, with some folks seeing a generic "Android OS" entry taking up 500MB-1GB per month. Now I haven't seen any reddit posts about this within the last 8 months or so, so this may be fixed.
The other is that it doesn't seem like you can root a phone or switch to a different OS without potentially screwing up service. This is a mixed bag: I'm actually trying to get away from Google as much as possible due to their data collection. Granted, nothing says I have to use GMail (and I'm moving towards not using it at all), and some of the more egregious things (the various services that involve always listening) can be disabled. And I'm not 100% sure there's a significant difference between giving a lot of this data to Google vs. giving it to Verizon or some other carrier. On the other hand, even if I'm not using GMail for e-mail, your phone is tied to your GMail account.
But I'm also not sure what the alternative is. Verizon sucks as I said, but the only other companies in the same ballpark price-wise as Fi are these smaller no-name ones, and it's a roll of the dice either way.