Personally I don't think the whitespace is that much of a problem. Certainly I don't think whitespace makes infix less readable; it probably makes it more readable if anything. And it don't think there is a terribly appreciable difference in typing or reading time because of the extra characters. (Arguably the space bar is the easiest key to hit on the entire keyboard.)
While I wouldn't necessarily miss punctuation characters that much, I don't really think it is worth it just to remove the whitespace from infix expressions. You could interpret +-/* as separate in infix expressions only, but I think that creates unnecessary uniformities in the language.
And I do think that math matters. Maybe there are a lot of areas in which you wouldn't really gain much with the infix notation, but exactly the opposite can be said for other fields. I've been working on simple 2D game in CL, and all the math expressions were getting a bit annoying. I would love to try rewriting it in Arc if Arc ever got bindings to any good game libraries.
Sorry for my repetitiveness (said the same elsewhere) but The Lisp Way when you need a domain-specific syntax is to implement that with a macro and then use the syntax wrapped by the macro. Then Peter does not need to rob Paul (in this case by impoverishing the Arc naming syntax to get math syntax).
If you will simply go without not having whitespace between operators, then you doesn't need to disallow cool characters in symbols or add macro calls in front of all the infix expressions in your code. Honestly, all you save in whitespace you probably spend immediately in having to make the call explicit. I like that the current system integrates infix math seamlessly with s-expressions, that's why I spent my time writing that code. (Admittedly, the infix parts aren't perfect, but the integration itself is fairly seamless.)
I did look at some of the CL infix packages. And if I didn't have programming assignments to work on I might consider porting one.
