[bylo]

I've been using Google Fi all summer to roam in the US and EU. It's a great solution IF you can qualify and your usage needs are compatible with Google's pricing/billing policies. Reliability, speed, coverage, flexibility, etc. have been great.

1. You need a US address and USD credit card to get a GooFi account. Although I'm based in Canada, I have both. That may be a barrier for many others, especially in the EU.
2. Activation works best when done in the US (or in my case from Canada within a kilometer or two of the US border accessing a US cell tower.) I had problems trying to activate from UK. Others have reported success from other EU countries. YMMV unless you do this in the US.
3. The selection of supported phones is limited. Other phones will probably work.
4. The base plan charges USD20/month for unlimited calls/texts in the US plus USD10/GB data. Fortunately (a) you can suspend/resume service at any time and (b) they prorate service time to the minute and data use to the MB. This works very well for occasional use.