I use Common Lisp for most of my daily programming, and SBCL is a big reason why. Once you get over the initial hassle (getting used to the Emacs+SLIME tool chain and learning to read the compiler diagnostics) it really gives you the productivity of Python with the performance of C++. And a lot of that performance is thanks to the tireless effort of the SBCL developers, who have been churning out a new release every few months for the last decades.

Kudos to all SBCL contributors!