For an user of a product/service, this is bliss. For a hacker, it might get tricky.
Now, considering the fact that this is all open source, the huge wall you’re talking about is just a matter of perception. You’re free to debug and go with it as low level as you need.
It’s also worth observing that Meteor is not presented as a “framework”. The comparison with Rails was introduced here, on HN. They say it’s “a set of new technologies”. I guess this implies loose coupling, which is a healthy paradigm when applied to components/modules/objects of a development ecosystem.
If only Meteor were nothing more than a proof of concept, it would still be mind-blowing.