Doing some testing on the plugin and am getting a minor error that you might want to address.
Looks like the private class variable does not have an underscore, but the reference does have an underscore.
error type: [8] Undefined property: autoptimizeStyles::$already_minified file: D:\web-site-dev\bling-transfers.com\wp-content\plugins\autoptimize\classes\autoptimizeStyles.php line: 329
[02-Apr-2015 12:52:04 UTC] Debug Trace:
......autoptimize.php at line 265 function n/a ()
....n/a at line n/a function n/a (?)
.....functions.php at line 3269 function n/a ()
......n/a at line n/a function n/a (0=)
.......plugin.php at line 496 function n/a (?)
........load.php at line 613 function n/a (0=shutdown)
.........n/a at line n/a function n/a ()