Yeah, I agree the seats aren't so comfortable. They're overly firm. I'm dreaming of owning E or S class in the future and hoping/wishing the seats are like arm chairs.
The seat for me (young, healthy), does irritate on longer journeys, I find there's a certain sweet spot on adjustment and when I get it perfect, it's alright, but it's very finicky, slightly out in one way or another and back ache after a while.