My one counter argument for 1 and 2 is that with infix, I'm forever trying to remember precedence rules and in my own code, just end up wrapping everything in parentheses anyway, to be sure. In lisp, the ordering is always explicit.

For 3, that's one reason why I like Clojure's syntax: it has just enough extra syntax to break up the code and provide visual cues, at least for me.

Re 4, sure, you can even enable macros without homoiconicity, but with s-expressions, I find it to be mentally much simpler because I can just write a template and fill in the gaps and its natural since my code is in that form already. Overall, though, in all but a few cases, I think macros should be avoided in favour of pure data structures and functions, when possible.