I often take the Shinkansen so use this express booking app.
It’s slightly inconvenient that a ‘JR Central’ credit card was needed to use the service, and a dedicated IC card necessary to take the train as well.
Afterwards, even though I could use it with a credit card other than JR, the IC card wouldn’t work with anything else. What’s more, when getting off at Shinagawa and switching to the conventional JR line, you can’t exit through the gate as usual using the EX-IC card and iPhone’s mobile SUICA. Normally you can use the EX card with SUICA and PASMO by putting them together. It’s necessary to handover each one, along with the iPhone, to a member of staff at the gate, which was really cumbersome. It would be great if I could only take the Shinkansen just by SUICA.

And found a​ ​long-awaited service​ ​has begun.
However, it is different from the old service. First, there’s the price. Of course, for a genuine service, the EX reservations are cheaper, and where a ‘Green’ seat becomes free, ‘Green Points’ are added for every ride (though ‘Green Points’ are not covered by non JR credit cards).
Do you need to shown it at the ticket gate, and will it allow an upgrade to the Green car 2 or 3 times a year for free?
I’ve registered with Smart EX for now as well, but guess I will wait and see what happens before switching.