A common question is how to compare Fedora  and Debian  in terms of recent updates and support. I think that Fedora Rawhide and Debian/Unstable are fairly equivalent in this regard, new upstream releases get packaged quickly, and support is minimal. They are both aimed at developers only, but it seems that a reasonable number of people are running servers on Debian/Unstable.
Fedora releases (previously known as “Fedora Core” and now merely as “Fedora”) can be compared to Debian/Testing. The aim is that Fedora releases every 6 months and each release is supported until a release two versions greater is about to be released (which means that it’s about a year of support). The support however often involves replacing the upstream version of the program used to make a package (EG Fedora Core 5 went from kernel 2.6.15 to kernel 2.6.20). I believe that the delays involved in migrating a package from Debian/Unstable to Debian/Testing as well as the dependency requirements mean that you can get a similar experience running Debian/Testing as you might get from Fedora.
Stable releases of Debian are rare and the updates are few in number and small in scope (generally back-porting fixes not packaging new upstream versions). This can be compared to Red Hat Enterprise Linux (RHEL)  or CentOS  (a free re-compile of RHEL with minor changes).
Regarding stability and support (in terms of package updates) I think that Debian/Stable, RHEL, and CentOS are at about the same level. RHEL has some significant benefits in terms of phone support (which is of very high quality). But if you don’t want to pay for phone support then CentOS and Debian/Stable are both good choices. Recently I’ve been rolling out a bunch of CentOS 5 machines for clients who don’t want to pay for RHEL and don’t want to pay for extensive customisation of the installation (a quick kickstart install is what they want). The benefit of Fedora and Debian/Testing over RHEL, CentOS, and Debian/Stable is that they get newer packages sooner. This is significant when using programs such as OpenOffice which have a steady development upstream that provides features that users demand.
If you want to try new features then Fedora and Debian/Testing are both options that will work. One reason I had been avoiding serious use of Debian/Testing is that it had no strategy for dealing with security fixes, but it seems that there are now security updates for Testing  (I had not realised this until today).