I thought I'd balance out my earlier criticism of Arc with some quick thoughts on what I like about Arc.
The main thing I like about Arc is that it's a Lisp, which is to say, it uses S-expression syntax to express programs as lists. I agree with Paul that this is one of the most colossally good ideas ever to emerge from a human brain. S-expressions are the Right Thing.
The next thing I think I like about Arc (I say "I think" because this capability is only hinted at in the current documentation) is the way it tries to integrate into the web, and in particular, the way it seems to fold control-flow for web pages into the control flow for the language (like this for example). The seems to have grown out of Paul's viaweb days when he first used the idea of storing web continuations as closures. Integrating that idea into the language and having the compiler automagically generate and manage those closures behind the scenes could be a really big win.
I like the general idea of getting rid of unnecessary parens, though I think this is not as big a deal as Paul seems to think it is.
I like the general idea of making programs concise, though I think this is fraught with peril (APL anyone?) and Arc could do a better job in this regard than it does. (More on that in a later post.)
I think the kerfuffle about Arc's lack of support for unicode is much ado about nothing. That's obviously a first-draft issue, and easy enough to fix.
Finally, I like that Arc is generating a lot of buzz. Getting people interested in Lisp -- any Lisp -- is a Good Thing.