When you read while lying down, you tend to grab these devices at their base. At least I do. When held this way in portrait mode, a longer screen would move the center of gravity higher. While that isn't a big issue with smaller displays, as the screen size goes up, it becomes more of an ergonomics issue.Normally as a developer, I'd prefer 16:9. Laptops, desktop monitors are all going 16:9 and haven't looked back at all, so knowing there's a standard configuration is helpful when designing. However, the resolution is also important, perhaps even more so than the aspect ratio. Anything with a 480 pixel dimension is not going to cut it. Websites, for example, are now designed assuming at least 800x600 resolution, with assumptions of 1024x768 being more and more common. A portrait mode of 480px's wide is practically useless in web browsing, unless you like sidescrolling all the time. Even if sites are shrunken to fit the 480px width, the amount of shrinking required to go from their 1024px or 800px width designs to fit 480px could make them either unusable or unattractive.