Is there a reason l3doc.pdf is not yet included in the l3kernel
distribution on CTAN?  Is it still too experimental to suggest for
wide-spread use?

Also, when typesetting it on my own system, I get this error message

(./l3doc.ind [47]
! Misplaced alignment tab character &.
l.9   \item \verb*&\&&
                      \pfill \hdclindex{1129}{}{0}, \hdclindex{1142}{}{0}
?

(This might answer my first question.)

—Joel