[baddox]

shouldComponentUpdate is nontrivial to implement when you're using mutable application state. I feel like all React tutorials should at least mention this, but sadly most seem to say something like "do not worry about performance until it becomes a problem, then just implement shouldComponentUpdate."

[i_s]

If you have a slow react component that uses mutable data structures for state, and implementing shouldComponentUpdate is hairy, you could always switch to using immutable data structures for that component's state instead. That change alone is very easy. From there, implementing shouldComponentUpdate is very straightforward.