Since nm are Now Marketing, unrelated to physical dimension, how consequential is this node shrink? It must have passed some threshold to justify new factories - what was it?
That's not entirely true. They might not decrease the minimum gate length, but generally the improvements made when bumping down the "nm" number has been a similar improvement as what making the gate length smaller would have given. So I don't find the numbering as misleading as others think.
It's not like any of us a designing gate cell libraries (well, I have, a very basic one, but I'm guessing most here haven't), and actually care about the gate length.
Using the minimum gate length as a naming scheme was always been a proxy for things chip designers actually care about: logic density, timing, power, etc.
It's hard to directly answer "how consequential", but it seems like it could be as significant as the step to TSMC 16nm.
Next smallest is picometers, 1000pm = 1nm