I've got one I bought in the USA to use in the hire car.
As per the other 2 Iv'e seen, they're s****.
Interestingly I've noticed Dixons have been selling them for a few months now so I (wrongly) assumed the law had already passed.
Ofcom are right to allow them, they cause no interference as it's hard enough fetting it to transmit from your centre console to the radio in your own damned car, much less anyone else's...