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?

>>28
+ You do lose something when you lose pointers (especially in C)
What do you lose?

A quick question first: are you aware that The Standard says that pointer arithmetic resulting in out of bounds values is undefined behaviour (section 6.5.6.8)? Or are you one of those script kiddies who have not even read The Standard and whose notions of what C language is would rather fit a high fantasy novel, as indicated by your mention of "self modifying programs"?