OK, I pulled the trigger and signed up for Project Fi. 3 sorta free-ish Pixel 3XLs and a $200 credit for porting an iPhone. The maximum risk over 4 months, vs my existing Sprint bill, isn't much more than the $200 service credit. So even if we can't figure out data discipline well enough to make Fi work long term, I'll come out about even cash-wise on the plan itself over the 4 month commitment.

One thing to note: even though the phones are backordered and won't arrive until December 10th, I had to front the payment and front the sales tax on all three phones. The gift cards appear to be issued after the four months, and do not cover the sales tax. In my calculations, I assume it will take me 6 months to consume a little under $3,000 worth of Southwest flights and an even flow of $500/mo.

They appear to finance the phones for "free" if you are willing to give 'em a credit pull.

So these aren't really FREE phones, but they're still good phones for pretty cheap and we'll have freedom to shop BYOD plans next year if we need to.