Hi
Important changes for spins include using the Koji build system to build
the images and LZMA compression to save more space,
http://www.serverwatch.com/news/article.php/3934251/Fedora-15-Spins-Custo...
""We wouldn't go through the effort of building the spins if we didn't
think they were useful for both building our community and to give
people a creative outlet to do what is best for them," Smith said. "It's
really hard to make a one size fits all operating system, so we found
that the spin process allows people to be more focused on what part of
the operating system they want."
Rahul