No direct experience, but I did read up abut it. It seems that the booths are equipped ith cameras which can determine whether you are solo car, Class 2 with single axle trailer other classes for motorvans and TA vans. That was the first let-down, I had hoped that by making payment easy for them they might have let every off as basic car. (see how unworldly one can become with advancing years.
The big problem, however, was that the radable tag has to be bought for quite a lot of euros. It also has to be placed inside the windscreen at the top on a clear area - my present cr has a sort of dapple pattern over some of this area. I came to the conclusion that if you were making several visits during the year, or were travelling solo (which makes getting out and going round to the booth or machine a nuisance) it could be worth while, but if the cost is computed in reasonable bottles of wine it didn't seem worth while - at least for me.
Google it and read the website - it will probably answer any other questions.