While my RH 9 server is working fine, it has become apparent that I'll need to go to Fedora at some point. What are the gotchas and how best to prepare my machine? Thanks

You would probably be better of doing a clean install, than an upgrade coz recent versions of Fedora are so technically different from Redhat 9 and a clean install will reduce the occurence of problems. Another good option to look at would be Community Enterprise OS, which is a very good RHEL clone.

I was going to start with Fedora Core 1 and work my way up. Is this a safe approach?

Fedora Core 1 is no longer being supported with security updates. Fedora Legacy hopes to fix this problem but I heard they have not been very timely with their updates. Fedora is also not really aimed at servers. I would suggest CentOS , WhiteBox Linux , or Debian

They are all much more stable than Fedora Core and much better when it comes to servers. Although Debian Stable would be a step down as it is more outdated (read: stable). For instance, it uses the 2.2 kernel. So, CentOS would probably be the best.

I have the same question.
I am not happy to hear that the upgrade path from RH 9 to Fedora is so rocky. In retrospect it was a real mistake to install RH 9.0. I have a nice, functional system that seems incompatible with all the good new stuff that's coming out.

For that matter, is Fedora all that great? It seems to have a larger userbase than RedHat 9.0 (for now) but it seems more and more that RedHat forked its own product line. The issue is not so much what works now, but will I be able to get support for it one, two, three years down the road. What will and won't be supported now seems to be the ad hoc decision of a community that isn't as anchored as the Red Hat community was before the forking.

If I'm going to go to all that trouble, maybe I should forget RedHat altogether and go with Debian or SuSE.

With SUSE you are looking at upgrading every 2 years or else paying hundreds of dollars. Debian is outdated and their newer branches don't receive proper security updates. With CentOS, you get 5 years support for free. I think Slackware is a good choice too, but its status is unknown right now, I have heard security updates are shakey.

I would personally recomment CentOS or buying SUSE Linux Enterprise Server.

Do a fresh installation on a separate machine and prepare that one in parallel. When you've set it up to your satisfaction, you can migrate your running server.

No, you won't. Simply because the life-cycle of the Fedora Core distributions is not that long (even the last Red Hat Linux releases were only supported for a year). And with a release-cycle of roughly six months, the Fedora Legacy project would soon need to support a dozen distributions if they wanted to support all of them for several years. There are not enough community resources to do that, and hardly anyone has enough interest in old releases of Fedora Core for such a long time.

Fedora Core 2 will be transferred to Fedora Legacy soon. Fedora Core 1, Red Hat Linux 9 and 7.3 are maintained by Fedora Legacy already to some degree. Whoever has interest in those distributions and still runs them and exposes them to the Internet, should join the Fedora Legacy project and contribute help.