I don't optimize for a specific device, not even for the device I have. I format the books hoping that they'll work fine in spec-compliant devices, even in future ones. This means I still use "font-variant: small-caps" even though ADE does not support it, and sometimes the illustrations don't quite fit the screen, but I expect a future device will have the option to zoom/scan the picture independently.
If you create a book with additional features not included in the ePUB format, please don't call the result an ePUB book
