Newbie question - using sysinstall "Upgrade an existing system" - easy?

[Oliver Iberien]

What actually happens when you use "Upgrade an existing system" in sysinstall? 
Do you end up with the X-server, etc., all functioning as before, or is there 
a lot of cleanup to do afterwards? 

(In my case, this would be from 6.0 to 6.1, whenever the release version of 
6.1 comes out. I am getting DMA errors in trying to install a second drive, 
and posts from this list give the impression that changing versions may make 
a difference.)

Oliver