I was also curious when I bought the $3 USA 1Gb data sim. I ran a few speed tests and the last one was 69Mbps down, and around 6Mbps up. That uses up data (Nearly 100Mb!), so I'm satisfied with the speed testing. I realize it will vary by country and carrier, but so does every other roaming data service we gamble on. The fact that they have AT&T as a roaming partner for the USA is encouraging, since it is a major carrier with very good national coverage. I'm looking forward to trying this in Europe and elsewhere as an alternative to several services I've used recently. I have also installed the $3 plan on my iPad Pro 11" and it works well there also. Easy Peasy purchase and setup is a real game changer compared to some others I've used. The App is simple and easy to understand without a lot of fluff, so you can find your way around in it without having to hunt.

BTW, Customer Service has been outstanding, they have replied to my emails quickly with concise info and understanding of my inquiries.

I always travel with a "Plan B", this will be my Plan A until it's been thoroughly tested and trusted.