I ride high-speed trains in Asia frequently (Taiwan, China, etc.). All have assigned seats in premium cabins (and some in coach). It works well.

The difference is that other countries' trains have uniform seating, mostly with all 2x2 or 1x2 forward facing seats, such that nearly all are identical and passengers have little choice other than window or aisle.

Acela First has the mix of seat types -- singles, doubles, double tables, and quad tables, where half the seats at tables are rear-facing. Being at a First quad with strangers is worse than being in a Business double, especially when your table mates are non-stop cell-phone users, have their computers and meals spread all over, running power cords from the aisle seats to the outlets. and constantly banging knees. That's why the mad scramble for seats, that is worst at NYP. And that mid-route boarders (STM, PHL, etc.) get horrible seats.

The downside to the assigned seating system will be, for example: Pax1 boards at BOS and has a "bad" seat. Pax2 exits from a "good" seat at NHV. No one else boards, so Pax1 takes Pax2's former seat. Then at STM Pax3 has Pax2's original seat assigned, and has to kick out Pax1. It looks like the F attendants will now have to add seat monitoring/dispute resolution to their chores.

Let's hope that the next generation of Acela first cars has standard 1x2 seating throughout, so all seats are essentially equal. As long as there are sturdy and sizeable tray tables, in my opinion there's no need for the large hard tables.