Tim Bray: At the moment, there doesn't seem to
be much agreement about what Media-type to use for RSS files.
Userland, which is kind of the RSS industry leader, serves them as
text/xml. Infoworld,
a fairly sophisticated tech pub, uses text/html.
Mark Pilgrim, a popular
blogger who thinks really hard about these things, uses
application/rss+xml.
It seems to me that it should match what you use on the
link tag.