In an interesting and unexpected twist, Opera Mini (not to be confused with Opera Mobile) has surprisingly been ported to Windows Phone and posted over at XDA. It comes from the Windows Mobile code but has an extra "layer" to interface/work on Windows Phone 7--that's the good news. The bad news is it can only run on devices with custom ROMs like DFT meaning interop and dev unlocked phones are out, for now.
The file is only 1.13MB in size and Windows Phone Hacker notes that "...the dev obfuscated his code. Thankfully, we already know how it works, which is surprisingly simple. Time to hack ;)" meaning perhaps we'll understand more about what is going on with this and what is not. What we can take from this experience is that Opera Mini could evidently be ported to Windows Phone, if Opera wanted to do so, but due to perhaps Microsoft blocking such an app in the Marketplace, not worth their effort.
We're sure we'll be seeing more on this project soon. Though we do have to wonder: compared to IE9, how good can this be?
Source: XDA; via WPSauce, Windows Phone Hacker