Face+palm
The OS isn't running off the web, it's running on web interface code, like javascript, CSS, html...
This was a super smart decision since sooo many more people know how to write webcode than they do cocoa.
Plus, what are you talking about? every demo I saw it was much faster and much smoother than the iPhone. Did you see the scrolling in the web browser? Ten times smoother than Safari, and you don't have to stop scrolling and wait for something to show up like you do in Safari. It's butter!
Over all it looks much more responsive than the iPhone, even with multiple apps loaded. And all the reviews are saying the same thing!