Any distro can be stable enough to be a server. SuSE 9.1 is not designed to be a server out of the box, but it IS designed to be stable out of the box. With Linux, as long as you don't install the "bleeding edge" of everything, then you will be stable.
The latest kernel releases and software releases usually present some bugs/instability. They may not be prominent, but they're there because we all make mistakes. You just have to know what you have installed and keep a look out for bugs/exploits in your version of the software. That is the job of system administrator.
So I guess my whole point here is that any distro is as stable as you make it.
