Gizmo has a faq post on upgrading HERE
Not much has changed.
I did it two years ago with very little problems. In fact the only problem I had was the redirector scripts trying to figure out what settings to use.
The only thing I did note on my upgrade was I used polls. The import kept the posts for the polls but the actual poll and results were gone.
There is really not a lot to salvage form the old control panel settings since everything is quite different other than view the vars files to cut and paste. But you could do that from the classic control panel since it will still be functional.