Hi
Since the beginning of this loong thread, a new kid was born:
writer2xhtml is a small extension (500k) which produces a nice valid EPUB out of any properly structured OpenOffice.org or LibreOffice ODT file. Free, opensource, multi-platform.
Best results are obtained when you care about using styles with OO. You can have reflowable and floating images, tables, endnotes, ordered lists, style-mapping, whatever...
Current version is
writer2xhtml.oxt 1.1.7.
http://writer2latex.sourceforge.net/
If you read French, there is also more info with my signature.