Hi, Yes, it is something everysite should have for a few reasons already mentioned but I'll itterate. 1) If included on your header/footer(every page basically) you now have 1 click away from any page that will provide a link to every page on the site (so basically every link is no more than 3 clicks away) 2) It helps get you indexed. Usually when you get spidered it's the homepage and maybe a few other urls and then it comes back for more later, and it does this until its been through everything but it only finds whats been linked to internally or externally. Having your sitemap ensures everything will be spidered atleast once. 3) Some users simply need it. Don't assume everyone can work a website... most people won't use them but some people do. Heck, even I use some websites sitemaps on occassions if their navigation is too confusiong or is just wrecthed (which is not too common but not rare). The HTML one is for your users, XML is for google. Why not do both anyways. Out of either of the two I'd pick the HTML one. That one will benifit both the engines and users at the same time.
I created a website yesterday. Got 1 indexed page around hours later. Once I created a sitemap.html, I got 130 indexed pages in a day. Amazing isn't it?
Also what is that ror.xml? What's the major benefit to have it? It seems to have a bigger file size, i'm afraid the crawlers might not like it.