I was the guy who came up with autobinding in older Reacts and I'm glad to see it gone. It might save you a few keystrokes but it allocates functions that'll never be called in 90% of cases and has noticeable performance degradation. Getting rid of autobinding is a good thing.
As much as I agree with the performance side here, I believe the usability for devs is an important factor. Let the users who really need that last bit of perf opt-in, and let everyone else just go along in blissful ignorance. And I am honestly alright if "opt-in" means use preact or some other project.
Think about the reasons jQuery and WordPress were popular, despite performance issues, they JUST WORKED for people. React is the jQuery of vdom projects, don't try to make it the something it is not.
Don't you think the fact that React.createClass() behaves differently than JS makes it less usable (i.e. more surprising) for experienced developers? The goal of React is not to fix JavaScript's warts, nor is its goal to make programming easier for non-programmers. I believe if this is the goal of your project the end result would look very different from React (probably would look more like Vue).
Where did we mention making programming easier for non-programmers? I think libraries should strive to be as usable as possible to _all_ programmers, which in this case means reducing or eliminating very common operations (such as binding callback functions). When we're talking about working on a large codebase, useless boilerplate is a legimate cost both in productivity and maintenance.
