I've read a few things on react fiber and am still not sure how this practically effects writing a react component. From what I can tell it is all internal and there is maybe one new lifecycle event. I guess I'm confused why this is not just a version number change.
It's a major reimplementation of the core algorithm. Fiber is just a name for the project, but practically it is just version number change that brings major performance updates.
Check this post out about the changes: