May is conceding
1) that within seven days of May agreeing a Brexit deal, a motion to approve said deal must go to the Commons
2) that if there is no Brexit deal agreed by 30 November this year, the government must seek approval for its next course of action from MPs,
and 3) May will consider how to capture Grieve's other demand that MPs and Lords must be able to instruct the government on how to proceed should there be no Brexit deal by 15 Feb 2019.
Arguably this transfers considerable power to MPs over the shape of a future Brexit deal. And it probably means that a no-deal Brexit is no longer any kind of realistic prospect.
It means that if May really believes she was able to put negotiating pressure on the rest of the EU by threatening to Brexit without a deal, she has lost that leverage.
In other words, one of her favourite catchphrases - that no deal is better than a bad deal - is dead
. And that will be official in just a few days, when the bill returns to the Lords.