Thank you for the very thorough response. While the lack of image, SVG and font support is unfortunate, you do cover a large volume of books one would want to create.
By "display fidelity" I meant "It looks on my screen the same way it will look on conformant Reading Systems". You seem to be going a different route though (not necessarily a bad thing).
The other thing that bothers me a bit is that a power user does not have direct access to the source code that will end up in the epub file. While most people don't need this level of control, some do.
Lastly, it's disappointing that you use a nice cross-platform editor like Writer from OpenOffice.org and then make your final converter Windows only.
