One problem with changing from HTML (or a content editor) to reStructured Text in Plone is that the text editor doesnt convert your old HTML docs to reStructured Text.
However, my experience so far is that if you copy the text of the page (not the code), click on the edit tab, delete the HTML code and paste the content of the page back in, it does a pretty good job of keeping the layout of the page. Paragraphs, bullet points and numbered lists are largely mantained. Of course, links images and preformatted text all have to be put back, but what can you do…