Worked well on a brand new installed 7.5.4 on a FC 3 installation. The upgrade to 8.0.0 was almost flawless. Then again, starting with an almost-empty database helps!
The only issue afterwards was to upgrade the old packages using yum and ART's RPMs (to more recent versions of almost everything ART has). Since ART does not yet support the brand-new 8.0.0, I was curious to see how bad this would damage a fresh installation of 8.0.0.
This shocked me for a bit when I got an error that "srv_bandwidth" did have the wrong default value. Fortunately, looking at a dump of the tables, I saw this was to the line on module_bf1942_servers that creates this column using as default ''; changing it to 0 made everything work well.
PEAR seemed to be a bit confused, though; after copying the Console and Archive folders from /usr/share/psa-horde/pear/ to /usr/share/pear, at least I could use PEAR to upgrade itself

After that, it seemed to work fine...
Now the final task to be done: upgrading PHP to 5.0.4 (apparently supported by ART). This will be a challenge...
However, all the issues I got were
not related to the 8.0.0 upgrade at all, but to further upgrades using yum and ART's RPMs, which are not designed for 8.0.0 anyway. Still, they work!
Caveat utilitor