The biggest issue from my perspective is that the labels don't immediately connect to any kind of easily-communicable qualia, so even if you know the correct label, you don't necessarily have a good way of connecting the label to the feeling. (That said, the only emotion I required outside assistance to identify was a generalized anxiety, which didn't feel at all like I expected it to. I expected anxiety to be definitively unpleasant, and it was merely ambiguously so.)