Check my other reply. React is great but I think you need to buy the entire stack since one thing leads to the other. "I'm already using JSX so why not add just this one more babel line and get free ES6. It's the last thing I'll add, I swear"
I thought React was designed specifically so you won't have to buy into the entire stack (unlike Ember and friends). I've used React components without ES6, using plain old jQuery and AJAX calls during component mount (and nothing else). I didn't feel any particular temptation to add more things. Okay I'm lying :) . It's tempting, but it's possible to do without.
I did. It's part of React proper and merely syntactic sugar over React.DOM calls. You can use React.DOM directly, but it doesn't really change your level of investment in the 'stack', IMO.