I'm a huge fan of verisimilitude, the to point that I simply can't design a dungeon (or castle, town, etc.) without its backstory and original function very much in mind. And as a player I find a sense of verisimilitude really helps me get into the game.
But that said, when I look back at my favorite dungeon experiences over 30 years of gaming, there is no correlation to how "realistic" the dungeon is. In the end, I think the verisimilitude helps the campaign, but has little effect on the individual adventure.