• If you use it for reading and browsing, roughly the size of a book seems sensible. To me, the current iPad seems a good size for this purpose, although Paul Miller thinks the iPad is too big even as a reading device.
• If you use it as a phone, you want something you can hold to your ear comfortably. The iPad is just too big. Anything much bigger than (say) an iPhone and you’ll need a bluebooth headset or accessory. More stuff to cart around.
• If you use it as a camera, you need to be able to hold it up to your face. Again, the iPad is too big, so an external camera would be needed and more stuff to cart around.

Steve Jobs clearly states that the iPad won’t get any smaller and that for many purchasers it will replace the laptop computer. But one of the strengths of the laptop is the relatively open connectivity provided for both hardware and software. The iPad doesn’t (yet) provide such an open plug-and-play system.

The iPad is a beautiful device but is not yet the ideal touch-screen device for me. If it’s going to be this big, it needs to be more capable of real work and not rely on closed proprietary OS features. Personally, I’d prefer it about half the size it is now, all ready to go everywhere with me as a phone, camera, browser, email client, and app platform with no other devices or accessories needed. Maybe I need to look to Android rather than iOS?