I think the size of the errata thread pretty clearly explains why the update has taken this long. That has also taken our limited attention away from Spell Law.
I think you are at a point you could probably draw a line on the errata so far, apply them, and then add any new errata to a new revision or a published 'errata doc'. The obvious stuff seems mostly found.
I agree that it is time to release what you got. It is possible to wait until all the errata for Core Law start to slow down to ensure you have captured as many errata items as possible before making the "perfect" physical book. Still, I think it is not the most effective path forward. I think it is likely that any important issues that have not been found so far will not be found until the other books are out.
Also, the likelihood that the other books will be fine without extensive scrutiny by the users seems slim if we consider the number of errata found in the first book. If there are fewer authors creating the text for those might make the next books more coherent, but the layout process has caused a number of errors on its own. The books will probably not be ready for print even if the text started as perfect; furthermore, having an errata-free Core Law, but the other books in need of massive errata will not look very smart.
The largest thing holding back my RMU enjoyment now is hesitation if I shall start to print the pages I need for the game or if I should wait until there is a fixed digital release. There are good reasons that people are talking about Ironcrown release speed as glacial. I want physical books as much as most people do, but more than that, I want digital books that I can print so I can play the game.
I suggest it would be better to release all the RMU books as soon as they are done with layouts and let us fans scrutinize them as we play the game. Releasing books that need extensive fixes before the text is done is not good PR, but Ironcrown spends years proofreading the text and still leaves lots of things that need to be fixed, feeding the narrative of the glacial release process.
In computer software, you often use a set release schedule when the improvements that are done are shipped on certain dates. Sometimes the number of improvements included become minimal, and sometimes they turn out to be more significant but having a release schedule that you follow builds trust that the remaining errors will eventually be fixed. If RMU should start to gain momentum, I think Ironcrown should aim for digital releases of all the books and tell the customers that there will be errata updates to those according to a fixed schedule. When the number of errata suggestions dwindles down, the physical book is released.