Opera Software today released a new Beta version of the Opera Mini 5 Beta as a native Windows Mobile executable packaged as a .cab file. This means that a JVM or Midlet Manager is no longer required to run Opera Mini on Windows Phones. Finding and installing a compatible Midlet Manager has been an issue for many Windows Mobile users. A native Opera Mini eliminates that hassle and should also provide better performance and integration with the OS.
Opera Mini is much easier on resources than Opera Mobile 10 so it should be an especially good fit for low spec devices that have trouble running the latest Opera Mobile. The Beta supports Windows Mobile 5 and 6 devices. I don't know if that includes Windows Phone 6.5 or not.
I don't have a Windows Phone so I can't comment on how well this works. However there's a lively discussion going on at the Opera Mini users forum on MyOpera. Many posters say it works great while others are reporting a variety of problems. That's to be expected, this is a first Beta of new technology for Opera Mini. If you have a a WinMo 5 or later device, give the native version of Opera Mini 5 Beta a try. If you encounter issues please report them using the Opera Mini Bug Reporting Wizard. Unreported bugs are bugs that don't get fixed.