I wouldn't ever dream of an OS update from XP to win8, I like Dch48 would only do a clean install (if I were contemplating win8) and that would include doing my usual preparation with drivers, etc.
My comment wasn't so much the technicalities of the update, but that MS are now saying it is an option, when it wasn't for an option to upgrade to win7 from XP.
To me that shows that the only reason for this change of policy is to finally try to kill XP. This begs the question why is it now possible when it was supposedly technically not possible to do this with win7.