Scott Turner commented on Quicklisp helps focus ABCL development: "You need to get authenticating proxies into Quicklisp, or else you're never going to get users (or statistics) from the majority of corporate environments." I've only had a few people ask about support for authenticating proxies, so it hasn't been a high priority to implement yet. Maybe that priority should change?
Are you in a corporate environment? Do you use Quicklisp? Do you want to use Quicklisp, but the lack of authenticating proxy support holds you back? Let me know in the comments, please.