Personally, I think all “new” PHP applications should be autoload aware.
http://www.brandonsavage.net/making-life-better-with-the-spl-autoloader/
Provided that the codebase respects its own standards, it really isn’t hard to do. The real tragedy comes when a codebase has sections which can not be readily streamlined by _autoloaders() (as in – breaks the standard). An unavoidable indicator of a messy codebase is too many exceptions to the rule of class naming || code inclusion.
Sigh.