Yes, the Feel At Home from Three UK feels like the future!
The experience is very, very good - invisible.
Assuming you are visiting one of the 16 destinations they cover, you don't need to do anything. No signups, no opt-ins, nothing. You just go and use your phone like you would in the UK.
I also never felt that they were throttling the connection in any way, but I never really tested this.
Plus you don't even need to be on a monthly plan, any PAYG has all the same benefits.
Assuming you are visiting one of the 16 destinations they cover, you don't need to do anything. No signups, no opt-ins, nothing. You just go and use your phone like you would in the UK.
I also never felt that they were throttling the connection in any way, but I never really tested this.
Plus you don't even need to be on a monthly plan, any PAYG has all the same benefits.
Edit: Added reference to PAYG.