What's the deal with Common Lisp?
CyberFonic: I'm no expert in any of the Lisps, but find that the learning curve with CL is massive.  Of course, the return on your investment in learning is huge as well.Depending on what your applications are, you might find something that really hangs together well, like newLISP a better fit.  And it's very simple to intergrate libraries written in C.