I think the online classes with ready-to-go coding insie the browser are something to be really excited about. They lower the barrier into programming by so many levels...
I agree. I LOVE the python-in-javascript REPLs, but so far NONE of them have console i/o. (Python's raw_input command isn't implemented, for example.) And that makes these a non-starter for my courses unless I completely rewrite all my assignments. And that's a HUGE time investment for an uncertain payoff.