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?

>>32-34
There is nothing "high fantasy novel" about writing self modifying programs.
... in Standard C. All of it is high fantasy. Because inline assembly and calling a function pointer that doesn't represent a function are C equivalents of deep magic and travelling through a wardrobe.

The first thing that comes to mind is that you would lose the ability to allocate data structure dynamically
Today I learned that I can't allocate data dynamically in Python, or that it has pointers. OK, let me rephrase, what do you lose if you turn C pointers into references, i.e. get rid of pointer arithmetic (while making array indexing a first class operation, obviously)?