I think people are reporting this relative to expectations rather than absolutely: they assumed it woudl be slower due to the lower cost and lower power consumption but the results defied that expectaion.
[1] http://www.anandtech.com/show/6422/samsung-chromebook-xe303-...
Also, this specific Chromebook is higher quality than those netbooks. It's more like an ultrabook in terms of design. Not to mention that it has twice the battery life of those netbooks under normal usage.