Since the Sony Reader seems to do so well with .rtf files (or so I hear), perhaps a link to the RTF official technical specs might be useful for future conversions, experiment and amusement. Onward e-ink warriors! :scholar:

RTF 1.5 specifications (http://www.biblioscape.com/rtf15_spec.htm)

Reader probably doesn't support the new features anyway, so just for the sake of completeness:
Version 1.6 (Word 2000): http://latex2rtf.sourceforge.net/rtfspec.html and http://support.microsoft.com/kb/269575/EN-US/
Version 1.7 (Word 2002): http://support.microsoft.com/kb/269575/EN-US/
Version 1.8 (Word 2003): http://go.microsoft.com/?linkid=5506909