Yep. It also had some differences in behavior. `createClass` auto-bound functions so that `this` always pointed to the component instance, and it supported mixins.
The React team now encourages functional forms of composition rather than use of mixins, so that's another reason why React.Component doesn't support them. The lack of automatic method binding has certainly been a major pain for people learning and using React, but it also means that there's no "magic" involved. The Stage 3 Class Properties syntax is the recommended way to ensure that methods are bound properly, and there's plenty of other possible solutions as well.
The React team now encourages functional forms of composition rather than use of mixins, so that's another reason why React.Component doesn't support them. The lack of automatic method binding has certainly been a major pain for people learning and using React, but it also means that there's no "magic" involved. The Stage 3 Class Properties syntax is the recommended way to ensure that methods are bound properly, and there's plenty of other possible solutions as well.