I found the SIM worked the best in the UK, fairly well in Ireland, and about as well or better in Belgium and Holland with 3G data (only place it said 4G was in the UK).However, my phone frequently lost services for a few minutes at a time, only to have coverage restored a few minutes later.

calling worked fine in London, but I could not use the calling feature in Paris/Barcelona

Just came back from my vacation and this SIM card worked well in Amsterdam and in Belgium.

Setup was easy and the card worked right away

I wasted over an hour of my life talking to customer service trying to make this work - not only are they unhelpful, they're kind of creepy (overly complimentary and weird)

The SIM worked great in England and Ireland for three weeks of travel