Hi,
I travelled on it once because standard class was completely full on the day we wanted to travel. It's slightly more spacious but you can still end up in seats like plane seats with just a table to lift down on the back of the seat in front. I thought all seats would be 2 opposite each other and a table in between. Saying that though when we went the carriage was virtually empty so you could sit more or less wherever you liked.
You get a meal but it's not a hot meal. A large roll, drink, yoghurt and fruit if I remember rightly - think I've missed something out but can't remember.
In my opinion if you can get one of the more comfortable seats in standard class it's not worth paying the extra for castle class. We've been since then on Eurostar and I booked standard class and we just took our chances re seating.
Joanne