Redirecting /sites/all/files
With Drupal 7, you do not need to do so!
Drupal file paths are stored using stream wrappers so you can simply change the folder path in Admin > Configuration > Media File System and move the existing files to new folder and you are ready to go!

You will see public://images/my.png like paths in files table and many other locations. These are the stream wrappers used in Drupal 7. 

However if your content has links hardcoded, they will not change. 
Try adding the following line right below the 

RewriteEngine on
RewriteBase /


lines. 

RewriteRule ^sites/default/files/(.*)$ http://www.example.com/files/$1 [R=301,L]