[korm]

> When using immutable data structures the comparison in `shouldComponentUpdate` is very cheap.

The equality check is always the same in pure components. Whether the data is immutable or not, pure components do a reference equality check. This will result in failing to update correctly with mutable data.

For simplicity, I guess you could go with PureComponent by default, and remove it as an optimization instead, which is what I've been doing with good results.