Welcome to MobileRead and congratulations of getting the Reader. We're glad that you are here.
I have enjoyed mine for many months and the reading experience IMHO just keeps getting better and better.
In addition to RTF, there are other formats that work well on the Reader. the
MobileRead Wiki Conversion page offers many choices of tools that can greatly improve the preperation and use of your own materials. From Stingo's MS Word Macro for formatting RTF files to Book Designer for producing LRF files (non-DRM BBeB files) to FeedBooks that produces wonderfully formatted PDF files for the Reader from out of copyright or donated books.