We are gearing up for Fedora 16. I was able to get most of my applications rebuilt on Fedora 16 Beta with nothing more than rpmbuild -ta XXX.tar.gz.
I had to add a couple of spec files to the older tar balls but in general it was easy porting dozens of RPMs to FC16 from FC12.
I hope to go live soon!
We ended up going CentOS 6.3 as FC16 went too avant-garde for us to use in production any more.
I collected most of the SRPMs rebuilt with rpmbuild --rebuild just fine. Many of the CPAN packages that I had build are available on many of the CentOS servers.