Maybe a secret positive outcome of using automation to write code is that library maintainers have a new pressure to stop releasing totally incompatible versions every few years (looking at Angular, React...)
Quite badly. Can't tell you how many times an LLM has suggested WORKSPACE solutions to my Bazel problems, even when I explicitly tell them that I'm using Bzlmod.
From recent experience, 95% of changes are good and are done in 15 minutes.
5% of changes are made, but break things because the API might have documentation, but your code probably doesn't document "Why I use this here" and instead has "What I do here" in bits.
In hindsight it was an overall positive experience, but if you'd asked me at the end of the first day, I'd have been very annoyed.
I thought this would take me from Mon-Fri if I was asked to estimate, but it took me till Wed afternoon.
But half a day in I thought I was 95% done, but then it took me 2+ more days to close that 5% of hidden issues.
And that's because the test-suite was catching enough class of issues to go find them everywhere.
Deprecated code is quickly identified by VSCode (like Text.textScaleFactor) but not the new way of separating items in a column/row by using the "Spacing" parameters (instead of manually adding a SizedBox between every items).
Coding with an LLM is like coding with a Senior Dev who doesn't follow the latest trends. It works, has insights and experience that you don't always have, but sometimes it might code a full quicksort instead of just calling list.sort().
Sometimes it ignores you but it works more often than not.