Right, as data literals my program is going to use they're great, I fell in love with Python a long time ago in part because of its convenient data syntax. Clojure's values-are-values philosophy is also amazing. How much value are they though as core syntax forms? Take keyword parameters for instance. In Clojure you pass to defn something like [a & {:keys [x y]}]. In Common Lisp, that would be (a &key x y). If you want to add default values, in Clojure you'd change to [a & {:keys [x y] :or {x 1, y 2}}]. In Common Lisp, that would be (a &key (x 1) (y 2)). They're both data structures, they both require interpretation by the human and the defn/defun implementation, they're both not eagerly evaluated like other uses of data literals would be (neither the sequences nor the symbols need to be quoted). Apart from Clojure strangely bucking tradition with everything by making the top structure a vector instead of a list, and a quibble of repeating yourself for default mapping, I don't really think one is definitively better than the other, but that also means I don't think Clojure improved on anything with that choice.
In Common Lisp the arglist is not a runtime datastructure, unless one uses something like APPLY. This means that the usual implementation (compiler/interpreter) will check the declared keyword arguments: is it duplicate, is it used, ...? For calls it can be checked if the keyword is known. That's usually all done by default.
