I agree. It is easy for us diehard Opera fans (user since 1997) to overlook the fact that we are among -- what? -- 1% of brower users. I value Opera for its features, not its rendering engine. Whenever I use Firefox or Chrome it is not as if I end up thinking "Gee, these pages sure look odd." More common, I find certain javascript scripts not working in Opera, necessitating (if I care) opening the page in an alternative.
My concern, justified or not, is just how isolated the MVC elements are from each other, and thus whether the rendering engine conversion will blow back to the interface in ways I regret. We will soon see.