>It's simple to use.
There are many Lisps that are simple and easy to use. Scheme, for one, is extraordinary simple and easy to use. Indeed, many colleges use it for their introduction to programming classes.
>It's small and self contained.
This could apply to any Lisp, but again is especially true of Scheme. Scheme is a very small language; the entire language can be built from 7 special forms. How much smaller can a language get? Even all the special forms required to build a "practical" Lisp like Clojure can be counted on two hands. Lisp, in general is a very elegant and self contained language. NewLisp's elegance and cohesion does not break new ground.
>It has a REPL and you can do introspection.
Every Lisp extant today has these two features. Indeed, introspection is inherent to all Lisps; when code is data and data is code, introspection becomes trivial.
>It has conveniently and reasonably named built-in functions.
>It deals well with a UNIX-derived file system.
Most Lisps have fairly nice pre-built functions for accessing files. Moreover, I don't want my programming language to become especially tied to a single platform, by making file-system assumptions that may not hold true on other systems.
>It's easy to pick up and start using, but you can still do fancy stuff.
Well, it is Lisp. The inherent abstraction of the language will mean that Lisp won't ever be as "beginner-friendly" as, say, Python or Ruby. That said, Scheme (especially Racket) does an incredibly good job of allowing total novices to build programs in a very short time. As far "fancy stuff" goes, I wrote a minimax chess engine with an interactive graphical front-end for a school project. I don't know if that's fancy enough, but it certainly seemed pretty cool at the time.
>The documentation contains worked out examples for every built in function.
Again. see Racket.
>The main developer is very responsive and helpful.
Well, here I must concede a point. I have no idea how responsive the developers of Racket are, for I never had cause to contact them.
>Trivially cross-platform with downloads, not compiles.
First, this is true of every JIT compiled and interpreted language. Second, its not as trivial as you're making it out to be. The user has to have the interpreter installed, unless the interpreter, libraries and script are all packaged together as a frozen binary of some sort.