${VARIABLE:-value} expands to the contents of $VARIABLE, if it exists, or to "value" otherwise. In this case value is ":", a bash builtin that does nothing. Effectively, the above sets PROMPT_COMMAND to run the autojump command, then to run the pre-existing PROMPT_COMMAND, if any, or a no-op.
3: We obviously dropped the ball on Windows QA. On the Mac, the Downloads window is cmd-shift-j, so I figured it was similar on Windows. Ideally we should make the keyboard shortcut configurable, but could you suggest a good unused Windows shortcut for the meantime?
That is indeed the "auth failed" error. Only two things I can think of: either you toggled the service slider to "Pinboard" without noticing, or Delicious authentication was down briefly. There was at least one other report of that:
Yep, the API documentation is gone; http://delicious.com/help/tools claims that developer documentation is coming soon. In the meantime, Pinboard's API almost exactly matches Delicious's, and its documentation is still up: http://pinboard.in/api.
Incidentally, the Delicious API is still working correctly (albeit slowly) for me.
It seems not to work with existing labels whose names contain a slash, even if you rename those labels. Also note that the parent label must exist, e.g. to have "people/friend-a" and "people/friend-b" appear in a hierarchy, you must also have a "people" label.
Command-T is a relatively new Vim plugin that does fuzzy matching on the entire path, giving greater weight to characters immediately following slashes or other word separators in the pathname. I've been using it for a few days now and can attest that it is extremely fast and seems to "know" exactly which file I want after just a few keystrokes.
While this is a beautiful interface, I often read things like "traversing a long source file trying to look for a specific method’s implementation" or "sick and tired of having to scroll through a raw copy of jQuery..." and am confused. Why don't more people use their text editors' search functionality to find a specific piece of code? I never find myself scrolling through long source files.