Wordpress is far and away superior to any blogging platform available on Ruby. It makes wonderful sense to write Wordpress templates in a somewhat more productive environment than raw PHP, then compile them down into something which requires no dependencies on the actual server. This gets you all of the many, many benefits of Wordpress (great plugin support! huge community! deploys at any commodity web host! SQL vulnerabilities patched weekly+!) while having your template development not hindered by copious amounts of spaghetti code.
It is also big news to folks who write a lot of templates, because something like this allows them to create a toolchain which spits out WP templates, as opposed to having to e.g. having a template framework that templates are built against. This means that they can do across-the-board updates much more easily. That's a huge win if, for example, you're a company that publishes 100+ templates and somebody reports an XSS vulnerability in a commonly repeated component of one of them. (I don't know if their other 99 templates are patched yet so I won't go pointing fingers, but suffice it to say this happened.)
It is also big news to folks who write a lot of templates, because something like this allows them to create a toolchain which spits out WP templates, as opposed to having to e.g. having a template framework that templates are built against. This means that they can do across-the-board updates much more easily. That's a huge win if, for example, you're a company that publishes 100+ templates and somebody reports an XSS vulnerability in a commonly repeated component of one of them. (I don't know if their other 99 templates are patched yet so I won't go pointing fingers, but suffice it to say this happened.)
+ Kidding, kidding. OK, mostly kidding.