What, you may ask, does 'continued regulatory alignment' mean (if that does indeed turn out to be the key line in the text)?
The answer, for now, is that it could mean anything you want it to mean.
The UK government could come back later and say 'oh, we just meant when it comes to car manufacturing standards - and that is the deal we want for all of the UK, so Northern Ireland will be no different'.
In which case, all today has done is to kick the border issue down the road. The Irish question would thus remain unanswered - and indeed just as difficult to answer as it has always been.
But I think this interpretation is a bit of a stretch. A much more reasonable assessment of what (appears) to have been agreed today is that Theresa May has now promised to ensure that Northern Ireland will, to all intents and purposes, remain as part of the Customs Union and the Single Market.
Or to put it another way; if the rest of the UK diverges (half the point in leaving for the likes of Michael Gove and Boris Johnson) and Northern Ireland does not, then Northern Ireland is in practice a place apart. But I think the impact is greater than that.
And here are a few reasons why:
In this 'place apart' scenario, the basic reality would be that Northern Ireland's interests might gradually become more closely aligned with Dublin than with London. And, crucially, Belfast would have a voice at EU Council meetings through its relationship with the Irish Republic that would be denied the rest of the UK. Over time, it is hard to see how this would have any other consequence but Northern Ireland being lured closer to the rest of the Irish Republic and away from the UK.
The idea of 'continued regulatory alignment' implies that goods will be able to move freely, as they do now, throughout Ireland. But the UK as a whole voted to leave the EU at least in part to 'control our borders.' If you want to know who is coming into your country, you generally have to have some means of checking. If there is not going to be a border between Northern Ireland and the Irish Republic, where will it go? I suppose - theoretically - you could have some joint border posts at Irish entry points (Dublin airport etc), but think about that for a moment and you realise it is a load of unworkable nonsense. So, if you want to know who is coming into your nation and you can't have a checkpoint on the 'true' border, then sooner or later you have to have one or more at the ferry ports in the UK. Whatever anyone says, Ireland will feel like one country and the rest of the UK another.
Irish nationalists will surely see today as a major step towards Irish unity. And I am not sure, in practical terms, how you could reach any other sensible conclusion.
Given points one, two and three above, it is incredibly hard to see how the DUP could possibly accept this. At least, if it did, it would be the most astonishing thing (aside from the IRA giving up its terrorist campaign) that I have witnessed in almost thirty years covering Irish politics. And if the DUP does not accept it, then we know it can and will bring this government down before any deal is finalised.
The SNP has already said that if Northern Ireland gets special treatment, then the Scots want it, too. After all they voted heavily to remain. And, just to add to the picture of unfolding chaos, the Mayor of London has demanded it for the capital, too.
So, in conclusion, I am amazed that Theresa May has agreed to this. I'll be even more surprised if the DUP - and quite a lot of backbench Tory MPs, for that matter - go along with it. I think you could even argue that it provides a long term road map to the breakup of the UK.
Unless, of course, it is not what it seems. As I said at the start, you could later argue that 'continued regulatory alignment' means almost anything. But if it is what it appears to be, then it is a very, very big deal indeed.