I maintain a sever that's currently RH7.3, and has a proprietary NUKE like 
system that's meant specifically for RedHat.  I'm not sure how we'll be able 
to migrate this to a new base OS, even if it's RH9.  We do not have the 
option to build a second system and cut over to it when it's ready - we have 
the one blade, and that's it.  Doing a new OS install would either involve 
wiping the system and building a new one from scratch, or possibly me flying 
out-of-town to do the physical upgrade.

We'll wait and see what the developers of the proprietary system come up with, 
but it looks like a colossal pain.