Opera Mini uses the company’s own browser engine rather than WebKit, which is used by Safari. This results in many pages not rendering properly, or not in the original page’s standard fonts.
So it’s here, much to the chagrin of pundits who had probably already written articles railing against Apple blocking it from the App Store.
In any case, it’s here, and… big deal.
Honestly, if I still had my original iPhone I’d probably use this a lot when on EDGE. But for WiFi and 3G, the ugly rendering and security issues (everything is proxied through Opera’s servers, and there’s no SSL support) are not enough to me to compensate for the speed advantage.