I think this package should be in Basic.

What does it do? it makes hierarchial lists respond pretty well to
keyboard commands. 

As the most immidiately felt effect, in any image, it makes object
explorers fast and convinient. I think it should be a boon to users of
the StarBrowser, and also any other applications that use hierarchies. 

It fixes a big gaping hole in keyboard usability, which is really
important for us to improve, since it will make the platform more
attractive to experienced programmers that have come to expect that from
mature programming environments.

Daniel