What is difficult to understand? It is the evolution of a well-established product.
Power users in this thread are viewing an entry-level notebook through their speeds and feeds goggles. People say that it will only be good for browsing the web and sending e-mails - great, because that's exactly the audience that it is aimed at. The MacBook Pro line exists for those with more involved use cases.
...The iPad also browses the web and sends emails. For much less, in dollars, hassle, and weight.