... the question is whether this is a top feature or an "other" feature. Can someone do something cool with this right now?
It is highly important - for PostgreSQL hackers only (and it continues in better extensibility ever year, so paradoxically, it is not something new) - I don't expect so usual user can use it in next two years.
but I am looking for, so in early next versions some interesting bgworkers will be in core - scheduler, idle connection killer, multi CPU sorter, ...
So I am thinking, it should be marked as "other" feature this year.