I've been using Opera under its various forms for the last 8 years or so, and this 6th version of Mini was expected to finally deliver a "real" iOS experience, since Mini 5 didn't have pinch-to-zoom, for example. It's true that Opera Mini uses a specific user-agent that automatically identifies it as a mobile browser, therefore triggering websites into mobile view, but to me, it's an advantage, not a flaw: the pages are tailored for the screen, and you have minimal horizontal scrolling, if any. I've found mobile Safari to be faster that Opera Mini when first loading a webpage, while Opera is faster in pages you've already visited (easy, they're still in cache), but there's one point where Opera is really faster: in webpages rife with pictures. There, the compression Opera does on its servers prior to sending the webpage to the browser shows its usefulness. As for the "look-and-feel", to each his own, as always...
