You should enable debugging mode when you are developing your plugin. It generates a lot of errors and has some deprecated functions.
I want to give your plugin a shot, but I am still in developing phase so U have debugging enabled. This plugin just generates too much errors, I can not try it. I can't even see the menu properly.
Notice: has_cap was called with an argument that is deprecated since version 2.0! Usage of user levels by plugins and themes is deprecated. Use roles and capabilities instead. in /wp-includes/functions.php on line 3466
Notice: Undefined index: action in /wp-content/plugins/tantan-s3-cloudfront/wordpress-s3/class-plugin.php on line 70
Notice: Undefined variable: error in /wp-content/plugins/tantan-s3-cloudfront/wordpress-s3/admin-options.html on line 1
Notice: Undefined variable: message in /wp-content/plugins/tantan-s3-cloudfront/wordpress-s3/admin-options.html on line 3
And the list goes on. You should initialize a variable when before you use it.
Hope you fix the issues, I am really looking for a good s3 plugin.