>>A developer should always go for a 15.4 inch screen.
>
>Why only a 15.4 inch screen? Why not 17 inch?

In my experience, a 17" screen is too bi for a notebook. My screen is wide enouch and it fits in most notebook backpacks or cases (in my favorite one it just goes out of the specific cushioned-section, but it is still quite protected (deeper inside, not exposed).

A good friend of mine used to have a 17" Vaio. The macnine rocked, but it was like carrying a desktop around: heavy, bulky, special bags needed, etc. He has now a 15.4" Toshiba and he is very happy.

Hope this helps,