Where did you see the increased difficulty if you weren't using JSX?
It's not a huge deal, but I keep getting this sense that jsx is strongly tied to react and this reaffirms that they are going to keep it that way. I do trust the react team still, but it makes me weary of future releases.
In short, this is somewhat of a transition step for the (imo) even better way of specifying your render with pure vanilla js collections. This goes in the opposite direction of what you're worried about. You can view `createElement/Factory` as the stepping stone, with the _additional_ benefit of allowing you to use es6 classes very soon. Smaller API surface and + using more js features rather than library-specific ones; what's not to like? =)
As for your worries about JSX: yes, it does come from React since the beginning. But we've taken an extra step of making it clear that this doesn't have to be React-specific: http://facebook.github.io/jsx/. You can plug this in CoffeeScript. If not, see my previous point.
As long as we can always do something like
div className: 'foo',
span className: 'bar'
Custom className: 'baz'