Well the trouble with the Klingon appearance change is that there was a whole story arc about exactly why the ones in the original series had a different appearance - the failed eugenics project and subsequent plague. Now personally, I didn't feel that was totally necessary and could have just been ignored as being about production eras, as we pretended it was all the same species appearance, but they did do that and provided a detailed explanation. So to then ignore all of that and change it again is a bit jarring as I said.
The reason why it becomes an issue is that it suggests an ignorance and a lack of interest about what has gone before. That's a bit troubling. We shall see.