I've had good experience with Closure's cautious approach to parentheses. It's not radical, in that it's still basically parentheses but their nesting is great

I've had good experience with Closure's cautious approach to parentheses. It's not radical, in that it's still basically parentheses but their nesting is greatly reduced by combination of tricks: Flattening, if reversible. E.g. if something's always a list of pairs, then it's represented as a flat list with pairing inferred. Having shorthands in syntax, i.e. [a b c] is (vec '(a b c)).