The answer is PalmFiction. Does a better job with some RTFs than others. Like for example RTF is Nisus's native format so there's some formatting junk in there PalmFiction can't read. Word RTFs, oddly enough, look great. But at least you can read them no matter what made them.
PalmFiction is free. It's also open source and messy to install, like you have to make sure you only pick the English UI files or you'll get all the menus in German or Russian. Has a nice interface for a free, open-source sort of deal, though.
Documents to Go 8 *Premium* reads RTFs. Only the basic version comes with the Palms -- reads text, Word, Excel, PowerPoint, that's pretty much it. So I downloaded a trial of Documents to Go 9 Premium and for some reason that defies logic Dataviz has taken RTF support *out* of DTG 9 altogether. I would have to buy Documents to Go 8 Premium to even see how well it would work, as there is no longer a trial version of DTG 8 available. And they can forget that, so...
When I get a chance I'll just get out my original install disc and put my lowly basic version of DTG 8 back on my LifeDrive, I guess. DTG is a mess to uninstall, I tell you.