I'm on Fi and love it. The three networks mean that I don't get quite as much LTE as I did with Verizon or ATT, but its still 95% as much. but if you overlay the coverage maps of Verizon, ATT, and Fi, you'll find that you get more rural service (thanks to US Cellular). Its 2G and 3G, but at least it's service where the big two fail. In general, I would actually say that loss of service and dropped calls have been reduced with Fi compared to ATT. This includes the lake where I never had service at all, now I can get a few bars here and there.
In fact, in the three places I always had trouble, I now have 4 bars of LTE on Fi.
I got a Pixel 2 (not XL) and it is a nice downsize from my previous S5 Active. Great screen, unlimited free google drive, wicked fast processor, great battery. Its rare that I can't find a downside, but I haven't found one and I've had it since Feb.
Fi's service is great for me. Works in almost every country, it's cheap, and it operates completely in the background. The phones have no bloatware, no one from Google calls you trying to get you to upgrade with cable and internet, nothing. You give them a credit card number and it auto-drafts every month (my biggest bill was $46 but I'm not a data-heavy guy). There is an app on the phone already that lets you monitor your bill and data usage, but it doesn't beat you over the head with notifications or ads.
The transition to Fi was super seamless, but that might be because I had an android before. Super easy GUI, clear things like "do you want to install the same apps" and boom. 5 minutes. You order it, give them the PIN or password for your old service, and they do it all.
I would recommend it to anyone... who is willing to accept one of the phones they offer.
If you get it, request a free data-only sim for an old phone. Nice to have if you're in Latvia and your primary phone dies but you need to communicate or navigate.
Be aware of the fine print. It's not misleading or devious, just hard to comprehend and the website doesn't do a good job of explaining it. When you travel to foreign countries there is often a 20 cent per minute charge for phone calls, but most countries they allow free wifi calls. I spent the whole summer in Canada and made several calls, some wifi, some cell (hence the $46 bill last month), but I have loved every minute that I've had both the phone and the service. But data is the same $10/gb anywhere in the world. It's nice to know I can travel pretty much anywhere and the only extra charges I have to pay is 20 cents a minute if I don't have wifi for a call. In the past when I went to Canada, I was careful to stay on airplane mode all summer and not make any calls. This year I used it just like I would here in the states and it was STILL cheaper than airplane mode on ATT