Dear all, here are some poorly translated suggestions from a friend who tried the WS epub converter. He's a professional with epub and ebooks, so I trust him :-)

The problem is that I'm not sure at all if I translated well, 
as I don't understand what he says... 

Aubrey

- there are imperfections in the css:
* ex. in the td padding: 
padding: 0.2 em; the space between the value and the unity of measure can create problems in some ebook readers;
*  word-wrap:break-word; this is a CSS3 rule, I don't think it is used by ePub2...

* I would add a margin at the border or the page with the @page, or it could happen that the text goes directly to the border in the ebook readers... (especially at the top);
* tables with <td style="width:100%"> have content that sometimes goes out the screen;
* images (for ex. maps) are too small. 220 pixel on a 250dpi screen as the Kobo one means less than a stamp. 
I would go also with percentage measures to the screen dimensions, and not absolute ones.