(defun delete-blank-lines-or-char ()
  (interactive)
  (cond
   ((region-active-p) (delete-region (region-beginning) (region-end)))
   ((looking-at "\n\n") (delete-blank-lines))
   ((looking-at "\\s-*\n[\\s-]*") (just-one-space) (delete-char 1) (just-one-space))
   ((looking-at "  ") (just-one-space))
   (t (delete-char 1)))
  )

(global-set-key [delete] 'delete-blank-lines-or-char)

(defadvice delete-blank-lines-or-char (around smart-delete-parenthesis activate)
  (cond
   ((looking-at ")")
    (save-excursion
      (forward-char 1)
      (backward-list 1)
      (delete-char 1))
    (delete-char 1))
   ((looking-at "(")
    (save-excursion
      (forward-list 1)
      (delete-char -1))
    (delete-char 1))
   (t ad-do-it))
  )