Atom is still x86, but UNR has made some Atom-specific optimizations to the kernel. I don't know the details, but there may be some partial incompatibilities that prevent it working on some non-atom x86 cpus but not others.
I installed 10.04 netbook edition on an old Dell inspiron, and it didn't grumble. Didn't do any subtle animation effects either, but that wasn't a biggie. Was a little slow flipping between the global menu and other apps which was a bit annoying for a 1.5ghz laptop with 512MB of ram! I was alarmed to see the omission of virtual desktops, and menu integration was a little odd. The person who received their updated laptop appears quite chuffed, given the choice again I would have used bog standard Ubuntu, but I was hoping the netbook edition might have some sensible power saving features.
