Loading the fancy inspector overrides the SBCL specific EMACS-INSPECT method for functions. It would be nice if it didn't, but rather co-operated with it.
At some point in the past C-I worked on presentations, which it doesn't anymore. This was very useful, and it would be nice to have it back in the fancy inspector.
While I don't miss the full DWIM magic of C-I, there is one thing I would like there: if the point is at the start of a list starting with FOO, insert #'FOO instead of FOO in the minibuffer.
Cheers,
-- Nikodemus