Update: I did return, and when not busy it was a very different experience. Staff were more friendly, and got the order right. There had also been changes to the menu to bring in more interesting options. It’s still an expensive alternative to other sandwich shops, but much less frustration means you’ll feel you get more for that money. I have upgraded the score as a result.
Overall, the taste wasn’t bad, but this is expensive, and the rigidity of the staff might get your blood pressure up. I would say if you like the look of a fixed dish, then go for it, otherwise it might not be worth the aggravation.