Because it's not easy and they're still working on it, I suspect.

If the screen was much higher resolution (like the 1400x1050 on my tablet PC), you can just let the automatic layout policies of the toolkit handle appearance. EG, the logical nesting of

is good enough.

To fit a UI into 800x480 and give the level of polish we've come to expect, you'll have to have two heirarchies like that above. And when you switch from landscape to portrait, you'll change the parent of (for example) the message list and the active message GUI components so that they render correctly. You may do fancier optimizations, like laying out the message list in a completely different way and redrawing it.

Now that's for one application. Full portrait mode will mean doing this for the phone app, calendar, contacts, settings, app manager, browser, etc.

I think proper portrait mode for the browser is key. Put in a portrait keyboard and im happy. At the moment when Im in portrait mode I cannot open my bookmarks or edit the URL (the address bar disappears) and I need to turn it back to landscape to use those functions.

I also dont understand why its so difficult to render the screens for portrait - for 3rd party apps that were developed for landscape only - yes I get it - but for native apps like calender, mssgs etc why? The N97, though symbian, could switch between any orientation on ALL its native apps. Why is the N900 more difficult? (geniunely curious).

I'd also suggest a virtual nokia d-pad and buttons to aid navigating the device one-handed. The pad could auto-hide or go translucent.

It's not. It's just that all this work was done for the N97 before you ever saw it, so that it looked easy.

Yes, Nokia could have done this all off-camera for the N900 as well, but they didn't. There have been many threads discussing why, but it all boils down to the old triangle: time, resources, and functionality.

There's also the fact that adding more resources to a project to get one aspect done may slow down the project overall. This is a well-known phenomenon, best discussed in a classic of the software industry called The Mythical Man Month. See http://en.wikipedia.org/wiki/The_Mythical_Man-Month, and the book is well worth reading.

That would maybe be becuase it's a mobile computing platform that makes calls not primarily a phone!

For a start the N900 is less restrictive in how things can be placed, e.g. the desktop. There is also the issue of what rules are applied for rearranging controls etceteras when changing orientation? The OS supports the application making a decision on orientation change but implimenting that when there is a hardware keyboard in landscape mode adds some other interesting issues into the equation.

Finally - have you seen the difference in resources available to the Maemo team compared to the Symbian one? The Symbian team also had a starting point of an OS which had all the basics in so had time to play with the pretty eye candy - Maemo team are going to be busy with the basics of the OS and cellular stack before eye candy.