I don't play WoW, so I'm probably the last punter you should listen to, but...
There's a lot of confusion about the term 'netbook'. Some of the comments suggest we were assuming your choices were classic 10-inch, Atom-cpu netbooks, but as you've clarified, only the ASUS EeePC is an Atom machine, the others use Athlon dualcores.
That said, buying a netbook or a CULV-type subnotebook is principally about mobility right? Weight, size, battery life. I believe AMD's offerings suffer dramatically shorter battery life than most of the CULV notebooks. You've already remarked that you want the notebook principally for purposes other than gaming...
There are decent CULV 11.6-inch notebooks out there for less than $500. I missed getting the Gateway EC1830u (rebadged Acer 1810TZ) with Pentium 4100 for $430 at Micro Centre (blast!). I suppose the question comes down to: are integrated ATi graphics so much better than Intel's 4500HD to compensate for the shorter longevity and weaker processor of AMD notebooks? Bear in mind that WoW stresses both the cpu and graphics. Unfortunately I've not seen head-to-head benchmarks of this sort.