I won’t use it, its indentation is very off.

take here: b is the body of the lambda function, but its indented as if its the body of the `letrec`

    (syntax (letrec ((f (lambda (a ...)
              b
              ...)))

or here

  
(define-syntax aif  
  (lambda (x)  
(syntax-case x ()  
((\_ test then else)  
(with-syntax ((it (datum->syntax x 'it)))  
\#'(let ((it test))  
(if it then else)))))))

Quick feedback: you could show before and after for a small snippet in your README, maybe describe the algorithm being used, and mention what options are available to tweak the formatting (line length being the most interesting and overriding how certain “keywords” format probably being the next most useful).