As it stands now, the trade-off is some unfamiliarity and discomfort up front for rather elegant consistency for the entire time you use the language. When you're optimizing for the people who'll use the language, the former is a lot less significant. :)
One thing worth noting is that Clojure does introduce constructs which use square brackets, braces, etc. It's a little nicer to use brackets for grouping, in lieu of parens for lists or declaring function params.
The elegance seems to come from having a simpler parser, and one less thing to explain to people when they're learning the lanuage. As a user of a language and not a developer of a parser, the first doesn't concern me and the second should be trumped by long-term concerns. Using significant whitespace to eliminate syntax is elegant in its own way as well.
Again, maybe this is just because I'm not a lisper, but keeping implicit parens that follow a well-established pattern should be a trivial mental task for a developer. Could you provide a piece of lisp code as a contra example?
Ideal:
Less ideal: The clojure comp shortcut looks good to me, but why even need the outside parens if it was the only line in that block? Ideally, that should be valid as well. I know this kind of reduction won't work in a lot of cases, but I appreciate syntax sugaring like this where I can get it.