I use [] only in certain spots for my scheme code. For binding variables in a let-block and for cond clauses.

(let ([a 5] [b 6]) (display a+b))

I find this easier to parse mentally, but I can see why one wouldn't do it, especially for cond clauses where you might end up having to actually browse parens to add or remove before or after the ].

I use paredit now, so there is really no need for me to do think about parens much at all, but old habits die hard.