I wonder how the rates compare to Google Fi? (Which is also compatible with iPad, even if it isn't advertized).
In case anyone is curious, there's a list of compatible devices on this page: https://support.google.com/fi/answer/6330195?hl=en I didn't know this was a thing. Is it new?
Fi also supports additional devices using a data-only SIM, which doesn't cost any extra except for the per-GB data rates. No $15 surcharge just for the ability to use other devices, etc. Same thing with tethering.
edit: also, this isn't exactly new, Google Fi was introduced in October 2016. I've been using it since then with no problems. In fact, I once received a reimbursement for a short outage that I hadn't even realized happened.