During the ACL 5 port, I discovered that there was a change in the behaviour of format with respect to symbols. For example, (format nil "~A" 'x) will not return "x" whereas the old Allegro returned "X". This wouldn't matter much except that some of our macros will generate symbol names using the formula and therefore would generate mixed-case names. I think that I have found and fixed all such cases.
I implemented the ACTIVESCP package, which allows LISP to invoke scripts through Microsoft's ActiveScript machinery.