In a response to this previous post about the PSR-0 standard and why it might be "shortsighted", Phil Sturgeon has posted some of his own thoughts on the matter as a participant (and supporter) in the PHP-FIG group.
One of the fun things about trying to support the PHP-FIG and all the good its doing, is seeing blog posts written complaining about it by people that just don't know what they're talking about. I get involved in conversations on Reddit (dangerous I know) on a mission to understand the problems with its perception throughout the community, and try to make more knowledge readily available to avoid confusion. I put together the PHP-FIG FAQ and the rest of the group voted it in, which I believe helped a lot. Sadly some blog posts are sent out by people with a whole bunch of odd opinions that you just can't do anything about, so instead I'm going to respond with a play-by-play approach.
He goes through several of the points Tom made in his original post, pointing out places where the information was either misconceptions or just completely incorrect. He relates some of the autoloading suggestions Tom made back to things Composer can do and how this is different from "magic" on the part of the library user.
PSR-0 has its problems, but they are the two that I have pointed out and they are rather trivial. [...] If you'd like to add custom autoloaders to your Composer packages then go ahead. If you'd like to build your own custom autoloaders for all of your packages then you can do that too, but it ruins the entire purpose of what PSR-0 is meant to do. That's fine, because you don't need to use it, but I am happy as hell that PSR-0 exists and I wouldn't make drastic changes to it for anything.