I'm lucky enough to have been on over 800 different types of train, and never have I encountered a train so unapologetically diabolical as the UK Class 800s. Riding on them is an assault on the senses.
Stepping on-board, you are met with lights that are just too bright, and this is even worse in hours of darkness. It is genuinely unpleasant to have such bright lighting on a train that operates on a metro service, but even worse for a train that is very often used for long-distances.
The seating is pathetic. It was rubbish from day one, unusually upright and nowhere near enough padding. Then the seat cushions promptly went on to collapse, so now you just get to sit on a metal/plastic bar, which is pathetic for a premier rail service in western Europe.
Then there's the ride quality, and oh my god is it bad! Each unit seems to vary, ranging from "bad" to "shocking". It's common to hear loud underfloor banging sounds, or harsh lateral hunting for long periods. Drinks are often spilled and objects are moved around simply by being placed on the tables.
And to add to that, the interior styling is bleak and dull, which of course does not go well with the harsh lighting. Also the interior feels cheap, which makes sense because it is, and there are often loose parts or rattles.
I hate useless rancid these things so much, they're just awful in every way. I certainly don't miss them when spending time in other countries, which I tend to do a lot these days.