Universal support would be fine; very limited support (within one app) is fine; half-way support is very tricky. Say you have a platform where 20 apps support portrait mode and 20 do not. Clicking on an app in portrait mode icon in the Menu or on the Home screens, you can never be sure if the resulting UI would be 90 degrees around. And the Dashboard: say that you have three applications running that work in portrait and three that do not, what does it look like.

The Dashboard is probably about the single hardest UI piece to solve in cases where some applications do not support portrait mode. I've already heard good enough proposals on how the Home screens would work, but I haven't heard the same for Dashboard. You can be in landscape mode, enter an application, turn to portrait, zoom out back to Dashboard. First of all every app needs to activate themselves and rerender themselves in another orientation (not easy peasy if you have 10 apps open), then again, some do not. Or you can enter the Dashboard, then turn the orientation: everything rerenders? Are the thumbnails horizontal or vertical? Or a mixture of both? What happens with notifications, do they also rotate? Are some graphics in thumbnails just 90 degrees around, i.e. not updated? Does the view turn only after entering the next application etc.

If somebody has great ideas on how to visualize this, please contribute to Brainstorm and let us know.