One of the great side effects from Quicklisp to us as the developers of an implementation, is the fact that for the first time since my last 10 years of lisp hacking, statistics have been published regarding system downloads.
Within the ABCL community, this list has been picked up as a signal from users telling us what they find important: Starting from the top, we've started compiling quicklisp provided systems and fixing the issues we found. Mark Evenson is working to fix bordeaux-threads on ABCL. Ville Voutilainen implemented an implementation-specific extension to DIRECTORY in order not to resolve symlinks required by Quicklisp itself. While Erik Huelsmann has been working to implement trivial-garbage required functionalities weak references, object finalizers and weak hash tables.