Common Lisp for Schemers

What's the best way for a Schemer to learn Common Lisp? It seems like Scheme itself is a more beautiful language, but the efforts made by many implementations to make Scheme useful "in the real world" lead to a big ball of mud™. Does Common Lisp avoid this problem? Should I keep trying to learn different Scheme implementations instead until I find something I like?

>>18
Yes, it's well known that anaphoric macros are referentially opaque like that. That just makes them referentially opaque in general, but not generally. You could say the same about functions, some of which may alter external state. Anaphoric macros are, in any case, a novelty used used by a few Common Lisp programmers, most notably Paul Graham.

Your pedantic diatribes are unconvincing, but do go on if you wish, I'm patient.