Ok, we've been using Google Fi for a while when we are away traveling because they have the T-mobile wonderful feature where they do not charge for roaming.
However beware if you try to use their new group plan. We put two numbers on a group plan thus saving $5 on the second line (Instead or$20 per line, the 2nd line and above are \$15).
But this leads to quite a few strange behaviors:

1. When you try to resume the service, you get an email saying you are resumed, but the website and the Project Fi application says you are paused.
2. The phone itself says the SIM fails and directs you to the Google customer support, so it seems as if it doesn't actually come out of pause mode.
3. When you go to the individual phones on the plan, they say they are active (even though the main screen says they are not). But you cannot pause the service there it fails.

I'm guessing that I'm on the cutting edge with wanting multiple phones and pausing them individually. I do have to say the application itself has some cool feature:

1. When you start a chat on the web from your phone and then logon to fi.google.com from your computer, the chat session follows you from the phone to the computer. Wow that is pretty cool
2. Also verification of the phone and who you are is handled in band with a popup from the phone saying, are you really you. That's pretty cool.
3. Another way that it works for validation is that there is a "secret code" on the website, if you have logged in then it works.

The fix by the way is to back out of the group plan. You have to do this carefully:

1. Do NOT end a "member" from the main console. This will cause you to lose your phone number!!!
2. Instead to to the member phone and say I want to leave the plan. This reestablishes that phone an individual plan.
3. In about one minute all the phones will start to work normally and each phone correctly handles the pause/resume.
4. You will get a strange artifact in that the "minimum" data on the owner phone is set to the the say 2GB if you have two phones. That minimum falls to 1GB on the next billing cycle.

In any event, this is a reminder to me of how hard billing and provisioning software really is. Glad I could get back without having to put in new SIMs. That is by the way what the Google chat guy told me. But that's not true.