I have to say that for my (admittedly very specific) requirements Fi has been my perfect company.

I'm generally uk based, but my uk plan offers me free roaming in europe, usa, mexico, canada, oz and nz. My uk line is an esim, and Fi is always in the sim slot in my iphone. While I'm in the usa/mexico, Fi is active as a secondary voice only line in case people in the US need me with all data going through my uk sim. I'm heading to guatamala shortly and with a couple of quick menu options Fi becomes my main data and phone account.

I particularly like the pro-rata pausing of service, when I'm out of the US for a while, I just pause the US number and the billing stops.

I do notice that the voice quality on the Fi line is very noticeably worse then on my uk line even while Im in the states.