The biggest problem of the iphone is the low resolution:

Most websites are designed for 800 pix width. There is usually a menu on the left and some adverts on the right, so it is still possible to read the site with a lesser resolution if you scroll horizontally or zoom.

The iPhone does not have something equivalent to the "optimized view" of the N800. This means: many sites need horizontal scrolling. This can be done with your fingers, and zooming can be done with your fingers too. Very slick - BUT: if you open a link, the zoom level is restored to its default, and you have to zoom again by hand.

This kind of zoom/scroll/zoom/scroll is very tiring and clumsy in the long run. The iphone is slick for some short and quick web session, but not for longer browsing.