The gimmick of having just two actors (one male, one female) play all the adults was a fairly effective way of reminding the audience that it's the perspective of the teenagers we're seeing. But it was hard to have any sense of how old these children are supposed to be, with their mixture of naivete and worldliness.
As for the performances, most were fine, but I thought Steffi D (as Ilse) was a bit weak vocally. The scene stealer was Andy Mientus as Hanschen.
This got excellent reviews but, overall, it really was not my sort of musical.