Regarding my previous post about X-Sendfile and FastCGI improvements for Lighttpd, this feature was recently added in the Lighttpd 1.4.24 release. It is now possible to build an entire pseudostreaming system using Lighttpd and FastCGI, that is much faster than the previous mod_magnet alternative.

From Cody Robertson about 1 month later:
Well that happened a little too late :P