all. Because I was lazy, last weekend I finally did a two-stage upgrade from 7.10 to 8.04 and then 8.10, with zero noticeable problems.
The scary one is two independent reports of fstab corruption in the 8.04 to 8.10 upgrade. It is claimed to be unfixable by booting from CD, mounting the partition, and editing fstab: the editor saves but the fstab returns to the original corrupt state upon reboot.
Several reports of inability to use formerly working Japanese input methods. Several reports of formerly working xorg.conf suddenly reverting to VESA 1024x768x8 (or worse).
I don't use Ubuntu so this is all hearsay, but I do trust the ex-NetBSD dev to be reporting accurately. He's only having problems with his custom X11 keymap getting trashed, and something else relatively minor with Xorg.
And for that ML this is huge; I don't recall so many screams on a commercial vendor upgrade since Red Hat went from HJ Liu libc to glibc 2.