Scripts that do not want buffered output just define NO_OUTPUT_BUFFERING before including config.php.
The fileserving code now checks if the headers are already sent which detects misconfigured servers.
Even though I've tweaked this and done some polishing, there is still plenty to do on it now in HEAD, mostly to do with UI, usability and strings, so we'll keep working on it. Aaron already has a number of improvements to add to it.