I`ve read they are, and I`ve read they are not, and I`ve also read that they can be detrimental to SEO because of duplicated content of that in a standard XML sitemap...
Selected answers from the Dumb SEO Questions G+ community.
Ranu Jain: Hi Mattew,<br /><br />I don't use ROR sitemaps anymore. They were good at the time they were emerged, gradually they got dumped as there was no such benefit. In fact, ;people complained that they got into issues with crawling using them.<br /><br />I would say that just use the standard format ;XML sitemaps. ;<br /><br />Just my 2 cents.
W.E. Jonk: From the expert panel in this weeks SEO Questions hangout on air on 01:19:32 into the YouTube video: