But underneath the GUI, Red Hat has made other changes: ext4 is the default filesystem, NFSv4 is the default NFS protocol version, and NFSv4 is now supported over IPv6. In addition, Red Hat has enhanced the KVM virtualization framework and updated core components like the RPM (Red Hat Package Manager) subsystem.
One very compelling addition to Fedora is the boot.fedoraproject.org thin installation framework. This takes a page from boot.kernel.org and is essentially a long-distance PXE install option using gPXE that requires only a tiny image file to be booted on a system; the install commences from remote package sources. The image file will contact remote servers for version information, so you won't need to update the image file even as newer Fedora releases become available -- they'll appear in the available install list. The hope is to eliminate the need for DVD ISO image downloads to reduce bandwidth costs and speed up the installation time for new users.
All in all, Fedora 13 is a clean and fast Linux desktop distribution. You can certainly use it for server tasks, but there's little benefit in going that route versus CentOS or another server-centric OS. Fedora has always been cutting edge, taking advantage of the newest versions of an enormous number of installed packages (over 1,500 in the default install). In contrast, Red Hat Enterprise Linux is more staid, with a significantly longer release cycle, and thus more stable. I don't know that I'll be cutting over from CentOS just yet, since my main workstation is as stable as the Andes, but Fedora 13 makes a compelling case for a workstation rebuild.