I understand somewhat what Opera is trying to do here, presumably in the name of performance.  However there are two security risks that I am not willing to take by installing and using Opera on my iPhone.

All traffic is proxied through Opera's servers. It’s one thing for an app on the iPhone to query the web, talk to its own or others’ servers, but something entirely different for Opera Mini to proxy the entire web through its own proprietary servers. Opera gets in between you and every single URL out there, from your bank to your school to your doctor’s office. You never communicate with any site directly, only through Opera proxy servers that first go to that URL, get a page, recompile it into its own markup language, compress and send it back to the mobile client that alone can understand it.

Man-in-the-middle encryption. Opera breaks your end-to-end security chain.  Because all of your traffic is proxied, when you visit a site that is encrypted via SSL, Opera will actually decrypt our data before recompiling it and encrypting it again before sending the data back to your browser.  Something to consider when you do online banking from your phone.

Of course because of their proxy, you can forget about jumping onto your VPN and viewing sites on your company intranet.

-boogybren