This is as much a story of my upgrade as anything but there are some tips and questions embedded in it as well.
As I said the Slackware 9.1 to 10 upgrade went pretty smoothly, all the really vital things like the networking started up with no problems at all after the upgrade.
The two things that needed some work were the xfree -> xorg move and xdm.
After finding xorgconfig (thank you whoever it was) the basics of video configuration were quite easy. Just copying my xfree config file to xorg.conf worked reasonably well and I then ran xorgconfig to check it as much as to change it.
The next issue was that xdm didn't work, since I use a Win2k system to display my Linux desktop (via the Cygwin/X server) this was rather vital to me. I found that 'startx' would bring my xfce desktop up OK on the local display but xdm gave an error in its log file saying that XDMCP failed to open a socket with errno 97. A bit of investigation (Google search) suggested that this might be that the xdm I had was expecting IPV6. So I sidestepped the problem by trying gdm instead, this works perfectly and looks a bit prettier too so I'm happy. I did have a bit of a problem initially when trying to login on my Win2k machine but that turned out to be because I was typing away on the wrong keyboard!
The one remaining video issue is that I can't get the native video resolution that I want, the card supports the 1600x1200 that I want and so does the display but I can't get it to actually do it. The remote desktop via gdm is at 1600x1200 but when I fire up a local desktop I get only 1024x768. I've put the 1600x1200 resolutions as my first choice in the xorg.conf file, what is limiting it to less?