I've just noticed that the official Swift language guide has been updated. It now includes a number of additional topics on concurrency. There's still a long way to go here, but this is good progress!
I think the migration guide is still useful, and goes into a lot more depth in many areas. But, I'm very glad to see this is being filled in.
(However, I'm not glad to see "split isolation" used in an example: a type with different isolation than its members. The language supports this, sure, and it does have uses, but is a mistake 99% of the time.)
I think many people do have issues here though. And a lot stem from using concurrency without the compiler feedback enabled. This is one of the greatest things about this feature: it fixes a surprising amount of code that is wrong today.