Your suggested "primary design decisions" seem to concern exclusively syntax & reserved names for built-in operators. This is a very specific and very superfluous aspect, for the latter two are the thin outer skin of any programming language.
From what I have read, Arc goes much deeper in its design principles. Those can be enveloped as the thorough "bottom-upness" of design: both read & write access to the language, right through to its primitive elements.
And this is the direct result of Mr. Graham's popular relation of Arc's design philosophy (http://paulgraham.com/design.html): a programming language ought to strive to accomodate those who themselves are qualified to design languages, translators and compilers, among other things.
This is at the foundation of Lisp, and Arc is a promising language because its designers seem to have well understood that foundation.
What is left to add, though, are modern counterparts of those 1960-s innovations that made Lisp superior not only in principle, but in reality also.
