Many of the issues PG addresses with Arc are those he encountered as a professional programmer in Common Lisp - the project is more analogous to Clojure or Scala than Racket in that way. That's not to say that you can't use it. People have worked through SICP in Arc. The question is what makes this better than MIT Scheme or Racket?
I've read through PG's tutorial. It claims to be for anyone, but there's a lot of discussion about fairly specific Lisp idioms - I don't think it's all too beginner friendly. In fairness, introductory tutorials where the messy interwoven details of the real world are left out doesn't seem to be consistent with PG's thinking, I don't think he's a big fan of dumbing things down, but I could be wrong.
Unlike Racket, Arc is very much batteries not included. And there aren't libraries full of them. Almost anything you want, you will need to build yourself. It's the hard way that's harder than Zed Shaw. Think On Lisp sort of programming.
http://www.paulgraham.com/onlisp.html
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What the hell, I'll just go all in.
If you're serious about Functional Programming, then why not Haskell? The documentation and community is pretty strong and it forces you to think about side effects and use strong static typing.
I don't like Python. I've tried and I've tried. Parenthesis may be visually unappealing, syntactic white space is mentally unappealing. And the whole 2/3 incompatibility suggests IE 6 and Cobol [which I find Cobol actually interesting with it's focus on data and emphasis on readabiilty]. Maybe if I was doing scientific computing, I'd use Python, but only if I could not afford Mathematica.
To me, and one of the reasons I wanted to like Python is that I grew up watching Flying Circus in the 70's, turned my son on to Holy Grail when he was five [thereby giving him an excuse to blame me for his adult problems], and have the 16 Ton DVD's. But my snarky conclusion is that Python needs the gimmick to distract attention from it's warts. It just doesn't work for me, though. Spam and eggs is cute, but it the effort might have been better spent.
Python is better designed than JavaScript. But JavaScript is unapologetically kludgy as to merit respect.
I do like Ruby. It's design is elegant and for general scripting, it's going to be just as fast. Mix in mixins for objects and blocks for higher level function passing and it's got a lot going for it. One of the big things for me that it has over Python is explicit `end` statements for blocks - Python ends blocks by indentation which means that formatting errors can give GOTOfail type errors.
Coming back to Scala, it reminds me of ML. It has the same sort of light syntax. The only reason I wouldn't use it over Python is the overhead of the Java platform - if you've got Java's libraries, you probably don't need Python's.
If you're on Windows, then C# and F# and TypeScript make a lot of sense. Lot's of documentation, lots of libraries, solid IDE, and the equivalent of the JVM you get for free.
Prolog is pretty cool. I here Smalltalk changes the way people think about programming, and I've toyed with learning Drakon.
http://drakon-editor.sourceforge.net/