I'm still leaning toward a fresh install anyway, especially if I can have both 9.10 and 12.04.
I favor 9.10 so much, and my existing settings, mostly because I've worked so hard to make it stable. For example, I had quite a bit of trouble with my touchpad and the cursor moving all over the place, but I finally solved that with a synclient script (can't remember what file I put it in.) Plus my video was buggy, but I finally resolved that too (can't remember what I did now.) So that's why I want to keep my settings and am still considering the upgrade path.
But I assume that the kernel code has changed so much that I might not have the touchpad or video problems anyway, but I may have an entirely new set of problems. It might be misleading to say "problems". I'll likely just have to tweak it to get things the way I want them . . . like I did with 9.10. And everybody has to do that to some degree, so it's to be expected. Hopefully it won't be as intense as it was with 9.10.